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Dear Director,
After reading the final KNKT draft report KNKT.13.09.24.04 for
the accident involving aircraft
PK-KFC I have following information to show the report was not
conducted properly as all
information available was not used to create the report.
I feel the person who did the investigation left out key
information to show the procedures
were wrong for our school and the procedure of leaning the
aircraft was the only reason the
accident happened. The following information shows that the
procedures used by this school
are in fact in accordance with the aircraft manufacturer and
engine manufacturer approved
limitations and procedures.
Here is a list of the issues I have with the report.
Issue 1- Page 4. The Cessna Pilot Hand Book required rich
mixture on takeoff except for the elevation more than 3,000 feet.
Issue 1 Answer- In section 4 of the Cessna 152 operating manual
page 4-14 under normal procedures for takeoff it states It is
important to check full-throttle engine operation early in the
takeoff run. Any sign of rough engine operation or sluggish engine
acceleration is good cause for discontinuing the takeoff. If this
occurs, you are justified in making a thorough full-throttle static
runup before another takeoff is attempted. The engine should run
smoothly and turn approximately 2280 to 2380 RPM with carburetor
heat off and mixture leaned to maximum RPM. See Figure 1. The
engine at maximum power can only produce 2280 to 2380 RPM. We had
constant engine
roughness before each takeoff since the use of MOGAS began. This
is found in the aircraft
maintenance documents and journey logs which justifies the pilot
to lean the mixture for
maximum RPM before attempting a second takeoff.
In the Cessna POH in section 4 for Fuel Saving Procedures for
Flight Training Operations paragraph 3 it states 3. Lean the
mixture for maximum RPM during all operations at any altitude,
including those below 3000 feet, when using 75% or less power. See
Figure 2 The Lycoming Operators Manual for the Lycoming O-235
states that at 2800 RPM the engine
will produce 100% BHP and will only produce 75% BHP at 2500 RPM.
These tests are conducted
at the standard temperature of 15C which will give higher
performance numbers than at the
temperature/dew point at the time of the accident which was
25C/21C 1013 hpa and a
density altitude of 3334 at the indicated altitude of 1500 MSL.
At sea level the weather was
reported at 28C/24C 1013 hpa and a density altitude of 2042 MSL.
The weather information
was not included in the report from the KNKT. I have added the
weather to this report for 12
September 2013 as figure 4.
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With a density altitude of 2042 MSL at takeoff, the airplane in
the temperature of 28C could
only produce 70% BHP and well below the 75% bhp for leaning the
aircraft
Issue 2 - Page 4 The investigation did not find the record of
the performance record before and after the AVGAS to MOGAS. Issue 2
Answer All aircraft were repeatedly grounded for rough running
engines beginning 09 June 2013. The conditions became worse and
worse. Instructors and students began to complain to maintenance
about the issue of the fuel. Maintenance informed the Principal
that the fuel was causing the plugs to continuously foul. The
response from the Principal was If someone wants to use Avgas they
can pay for it. Here is a list of maintenance discrepancies by
aircraft. This list was not included in the report to show there
was a history of engine issues with all aircraft in the flight
school.
PK-KFA:
On June9, June 10, June 11 and 12 the aircraft was squawked for
loss of power. The cause of
the loss of power was the sparkplugs had deposits on them and
needed to be cleaned. On 12
June the aircraft also had high oil temperatures.
On August 1 the aircraft was grounded for high oil temperatures
and we removed and replaced
the Oil Cooler as we thought that may be the issue. PK-KFA
continued to have high oil
temperatures after the new oil cooler was installed, but not in
the red.
PK-KFB
On 30 August the aircraft was squawked for a rough running
engine and the plugs were
cleaned.
On 11 September the aircraft was squawked for rough engine and
the spark plugs were
removed and cleaned. The message I received via text from the
instructor pilot was as follows
e have a problem with Charlieclmbing no more than 200 fpm and
with full throttle in straight
and level no more than 2200 RPMcan we use alfa even if it is not
dispatched? See Figure 8.
The constant removing and cleaning of the plugs caused the #1
cylinder plug hole to become
unserviceable and the aircraft was grounded until the heli-coil
kit arrived to fix the aircraft. It
was down for 3 weeks.
PF-KFC
On 7 September the aircraft was grounded for loss of power and
the Sparkplugs were cleaned.
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On 11 September the aircraft was squawked for loss of 200 RPM
during the run up.
Maintenance replaced 2 sparkplugs and cleaned the others due to
deposits on the sparkplugs.
On 12 September PK-KFC went down due to engine failure which was
caused by detonation.
PK-KFF
On 28 July PK-KFF was grounded for right magneto dropping to
many RPM during the run up
prior to take off. The mechanics replaced 4 spark plugs due to
residue on them.
Issue 3 Page 10 Item m. There were no evident of engine
performance record before and after changed the AVGAS to MOGAS.
Issue 3 Answer As seen above from the maintenance reports from all
of the aircraft performance was lost and several reports of power
lost in flight. PK-KFC was grounded twice in the preceding five
days due to engine roughness. Issue 4 Page 10 Item 5 The takeoff
Fuel Mixture policy taken by management was differed with the Pilot
Operating Handbook for Cessna 152 Issue 4 Answer - In the POH it
states Lean the mixture for maximum RPM during all operations at
any altitude, including those below 3000 feet, when using 75% or
less power. This is the same POH that is in the aircraft now and is
the same POH that the investigator used for his report. See figures
2, 5, 6, 7 Issue 5 No mention of the age of the fuel was mentioned
in the report. Issue 5 Answer - See figure 7. Fuel was delivered to
FlyBest Flight Academy was 24 April 2013. When I told the KNKT
investigator on 5 November about the information I found he said he
tested the fuel and found it to be of good quality. I told him that
the fuel could not be good since Shell Global states that the fuel
can only be stored for a maximum of three weeks. I explained to him
that, at the time I thought the fuel was delivered in beginning of
June and he said No the fuel can be stored up to 3 months. I asked
him if he smelled and felt the fuel and he replied No. I asked him
how the fuel can still be good if it was 4 months old at the time
of the accident and he had no reply. After further investigation on
my part I found the fuel was delivered on 24 April 2013. There is
no way to track the lot number on the fuel drums and the Principal
stated that fuel takes 2 weeks for delivery. If the fuel was
produced in mid-April then the fuel at the time of the accident was
24 weeks old which is 1200% to 800% over the recommended fuel
storage time of Shell and 200% over the storage time quoted by the
KNKT investigator. No attempt to find out the date of manufacture
was done for the fuel. In the report from Shell Global, Appendix C,
MOGAS is not designed to be stored for long periods. Within the
automotive world MOGAS is generally burned within a few weeks of
production so storage stability is not a concern. However, if kept
for longer periods, MOGAS can form sticky lacquers and gums that
have the potential to result in fuel injector or carburetor
malfunctions.
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The composition of Avgas is much more tightly controlled,
allowing fuel to be kept for months without deterioration
significant in aviation as it is not uncommon for an aircraft to be
in a hangar for several months with fuel remaining in the tank. I
have attached letters from the instructors stating what they found
during the preflight inspections of all the aircraft. Appendix D.
E. F. H. Issue 6 Page 13 Section 5 The accident pilot seem to be
not really understanding the risk of lean the mixture below 3000
feet. Issue 6 Answer - The Instructor pilot had over 1000 hours in
type at the time of the accident and over 2100 hours of total time.
The instructor is fully aware of the results from improper leaning
procedures. The instructor has flown for more than two years on
small piston aircraft using MOGAS. See Appendix H. All of the
instructors are aware of such results and if any of the instructors
had felt this procedure was outside a safe operation then they
would have expressed their disagreement with such procedures.
Synopsis
During the initial part of our internal investigation that began
on the 12th of September I stated to the head of maintenance and
the Principal I want a component test on the fuel. It does not
smell right or feel right. I want to make sure we do not have
contaminated fuel. No report was ever conducted or no results were
ever posted. During the investigation by the insurance company the
investigator noticed that there was no
scoring or scratches on the inside of the number 2 cylinder, see
Figure 3, which was caused due
to the fact that the engine stopped running instantly after the
detonation happened and did
not happen during the climb or over a long period of time. The
loss of power was reported the
day before as noted above. In the report from the Light Aircraft
Association it states If on the
other hand the fuel vaporizes from some hot spot or low pressure
area in the fuel system but
does not become entrapped, a stream of vapor bubbles will enter
the carburetor along with the
fuel, causing raised EGTs, lean running and reduced power, which
in the typical fixed pitch
propeller installation is evidenced by a loss in indicated rpm
and possibly puffs of white smoke in
the exhaust. The procedure of leaning of the engine was not the
issue of the detonation or
engine failure of the engine. The procedure of leaning the
engine has been in place since the
school started operating in January and none of these symptoms
began until June when we
began using the MOGAS.
Lidia Roset, the instructor of the flight where the engine
failed, said that when the engine
began to lose power she added mixture rich. The engine did not
fail. When she applied full
throttle the engine instantly stopped. This was caused by
partial vapor lock of the carburetor.
When she added full power as instructed to do by the Emergency
checklist during an engine
failure it further leaned the engine as more air was added to
the fuel to air mixture. Without an
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Exhaust Gas Temperature gauge on the aircraft Lidia Roset was
unable to tell the EGT of the
engine and therefore followed the emergency checklist perfectly.
The partial vapor lock with
the addition of throttle caused the detonation.
Every aircraft was noted to have a reduction in performance
later as the fuel was continued to
be used. All the pilots and maintenance noticed the fuel was
sticky and had a funny smell to it
as of June.
Maintenance said that when the MOGAS fuel drums arrived they had
corrosion and looked very
old and faded.
Since we started using the MOGAS we have replaced a total of 12
Sparkplugs due to deposits
on the sparkplugs. Since September 13th 2013 when we returned to
using straight Avgas we
have not had to replace any sparkplugs.
All of the symptoms stated above are from old fuel and started
in June when using the old
MOGAS we have in stock. All the squawks are from the aircraft
journey logbooks and Flight
Schedule Pro maintenance discrepancies. Every symptom associated
with old fuel is present in
the historical data of the aircraft and it all started in June
through September using both mixed
MOGAS/AVGAS and straight MOGAS. The mixing of AVGAS into the
fuel we have now cannot
be done as we cannot prove that it will make the fuel safe for
use. According to the
information we have this practice will not fix the issue as the
report from the Light Aircraft
Association states Assuming that your aircraft is cleared for
use with both unleaded Mogas and
with Avgas 100LL, there is no problem with mixing fuel of both
types in your tank. Note
however that even with just a small proportion of Mogas in the
tank, the vapour pressure of the
mixture will be almost as high as that of pure Mogas, so all
running on a mixture containing
Mogas must be carried out observing the operating limitations
for unleaded Mogas alone.
Prior to the use of the MOGAS we had no indication of abnormal
engine operations. There
were several other instances where the maintenance was alerted
to a rough running engine
and they cleaned the sparkplugs after the use of the MOGAS
began. Almost every flight we had
to clear the magnetos due to a rough running engine to remove
deposits from the sparkplugs.
When I asked the principal how long it took for fuel to arrive
from the time it was ordered she
said it takes about a week. I cannot verify the date of
manufacture of the fuel we have
received so far.
When I asked the maintenance engineers why we kept using the
fuel when it was thought to be
the cause of these issues I was told that they had notified you
several times about the fuel
being an issue and they were told it was too expensive to use
AVGAS and that if they wished to
use such fuel someone else would have to pay for it.
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Since we have switched back to pure AVGAS we have had only one
issue of power loss from an
aircraft and that was during flight when power was reduced below
2000 RPM during a day with
very high humidity which caused the carburetor to develop
carburetor icing. No student pilots
or instructors have had to clear the magnetos to burn any
deposits off the spark plugs since we
have changed to pure AVGAS.
Considering that the fuel was received on 24 April, see figure
7, and can only be stored only a
few weeks, according to Shell Global, see figure 1, before it
goes bad I cannot allow the MOGAS
we have in stock to be used in the aircraft no matter what we
mix it with. There will be no way
to guarantee the safety of flight with such fuel in the
aircraft. The following reports give every
indication we have seen in our aircraft since we first started
using the fuel in April.
Conclusion
With this knowledge and the research I have given to you by
Light Aircraft Aviation group, see
figure 1, and Shell Oil Company, see figure 2, and the Civil
Aviation Authority of the UK See
Appendix B stating that the fuel should not be used above 20C
due to the volatility being
higher, and the chance of vapor lock happening as well as
carburetor icing, the symptoms of old
fuel, and the fact that the fuel we have in stock was received
in April 2013, I sent an email to
the Principal, Appendix G, on 25 October 2013 with a report
stating that FlyBest cannot use
MOGAS anymore , even the MOGAS we have in stock and a different
solution needs to be
found, see appendix G. I received no response from the
Principal. On 3 December I resent the
same email and report and on the 5th of December I received the
response I fwd to Capt Budhi.
I am already busy with yearly report and budgeting things. See
appendix H.
The argument of financial savings for the company using MOGAS
instead of using AVGAS
weighs heavily towards AVGAS. During the months of January until
June we never had an
aircraft down or squawked for engine issues. Between June 9th
and 12 September we lost a
total of 99 flying days due to aircraft on the ground for engine
roughness issues. That is a loss
of around 400 flight hours. The cost of 12 sparkplugs of $29.83
each or, a total of around $358
and around 400 man hours due to the use of the MOGAS and the
loss of an aircraft reducing
our fleet by 20% is not efficient and is actually very
expensive.
This counter report is submitted to you for your reference.
Denis Boissonneault
Chief Flight Instructor
FlyBest Flight Academy
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Appendix A - Figures *1 See Appendix B - Light Aircraft
Association Report
*2 See Appendix C Shell Global Technical Aritcles
Appendix D - Raymond Duquesnays letter about aircraft
performance.
Appendix E - Stefano Marras letter about aircraft
performance.
Appendix F - Lidia Rosets Letter l about aircraft
performance.
Appendix G - Email to Karin Item about MOGAS usage.
Appendix H Email response from Karin Item about MOGAS usage.
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Appendix A
Figure 1
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Figure 2
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Figure 2 Continued
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Figure 3
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Figure 4
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Figure 5
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Figure 6
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Figure 7
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Figure 8.
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Appendix B
OPERATING INFORMATION UNLEADED MOGAS Issue 6. dated: 26th May
2009 This information is only applicable to LAA aircraft and only
those airframe/engine combinations specifically cleared by the LAA
for use with unleaded fuel. This document is to be attached as an
addendum to the Flight Manual or Pilots Notes of the aircraft
concerned or, in the absence of these, stapled within the airframe
logbook. 1. Obtaining and Storing Mogas It is essential that the
type of unleaded fuel used is to BS EN 228 and is the 95 RON
Premium Unleaded type. Check the markings at the fuel pump. LAA
have not investigated the older BS7070 specification fuel, which is
sometimes seen at the pumps although it is now superseded. On no
account use Four Star Lead Replacement Fuel which may be adequate
for gentle road-going use but is not suitable for aircraft, in
which the engine has to run continuously at high power setting. It
is always preferable to buy Mogas for aircraft use from a supply at
an airfield or a garage with a reasonably high turnover and from a
reputable supplier. We have come across problems in the past with
cut-price supermarket fuel of poor quality. In recent years, due to
pressures from the Green lobby to use bio-fuel, some petrol
supplied through the forecourts has had varying amounts of alcohol
added to it. The proportion of alcohol added is gradually
increasing over time and the number of outlets supplying alcohol
laced petrol is also increasing. Alcohol in the fuel can damage the
rubber components in the fuel system, and also cause problems
through progressively absorbing water which can suddenly come out
of solution later, flood the water trap and fuel sump and stop the
engine in flight. CAP 747, Appendix 8, General Concession 5 makes
it mandatory to check that unleaded Mogas fuel does not contain
alcohol before it is used in any group A aeroplane. The test method
for detecting alcohol in petrol as described in the CAA Safety
Sense leaflet 4b is not sensitive to alcohol levels of 5% or less,
the current maximum level likely to be found, therefore a test kit
has been developed that enables the detection of alcohol down to
around 1%. Alcohol detection test kits are available from Airworld
UK Ltd.
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Always store fuel in suitable clean containers. CAA requires
that fuel containers may be either metal, of up to 23 litres
capacity and fitted with a secure leak-proof cap (Jerry can)
labelled Petroleum Spirit, highly inflammable or if plastic, it
must be made for the purpose (complex regulations refer) and of no
more than 5 litres capacity. We are advised that the Road Traffic
regulations normally applicable to carriage of petrol by road do
not apply if the fuel is being carried for recreational purposes.
No more than four containers, which must be made specifically for
the carriage of petrol and have a maximum capacity of 20 litres
each, may be carried. If fuel is kept only for leisure purposes, we
understand that up to 270 litres may be stored in one premises
before having to apply to the County Council Petroleum Officer for
a license. Nevertheless if more than 15 litres is stored then there
is a legal obligation to inform the Petroleum Officer who must
inspect and approve the premises. He will require the fuel store to
be adequate for the job and to be equipped with a suitable nearby 6
Kg dry powder fire extinguisher. On the other hand, there is no
requirement to contact the Petroleum Officer if the fuel is stored
in the fuel tank of the aircraft itself. Nevertheless you should
use common sense and also consider the implications regarding
buildings insurance etc. Apart from the obvious safety
considerations, due to the short shelf life of Mogas fuel you are
advised not to store large quantities. You are far better off
purchasing small quantities of fuel as and when required, which
will ensure that you always use fresh fuel blended appropriately
for the time of year see section 7 below. 1. Records of Purchase
Find a reasonably substantial envelope and write the aircrafts
registration and the year on it. Each time you buy unleaded fuel
for your aircraft put the receipt in the envelope. At the start of
the next year, treat yourself to a new envelope and put the old one
into store for at least a further year. After that year has elapsed
you can then throw the old one away. The above procedure has been
agreed by the CAA to meet the intent of the Airworthiness Notices.
1. Quality Checks Despite the lack of aviation-type quality control
measures, over the years that four-star Mogas was being used in
aircraft there were few reports of problems due to contaminated
fuel from garage forecourts. It is likely that this record will
continue to improve due to more stringent standards of underground
tank installations and special tank connections to preclude the
possibility of the underground storage tanks being filled with the
wrong type of fuel. Nevertheless this is no excuse for lesser
vigilance on the part of the pilot, and all Mogas fuel
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should be poured into the aircraft via a fine-mesh or chamois
leather filter, and carefully sampled in the normal way. Watch out
for flakes of paint in the fuel from the insides of metal Jerry
cans. (When fuelling and de-fuelling, guard against flash fires by
electrically grounding the tank, funnel and can before transferring
the fuel, and avoid a brimming funnel. If the stream of fuel from
the source encounters the fuel in the receiver inside a closed
container, the fuel/air mixture will almost certainly be too
saturated to cause a fire should a spark occur. If, on the other
hand, the fuel stream encounters a brimming funnel in free air then
the petrol vapour in the vicinity may well be in the critical
region where the tiniest spark will cause a flash fire). If the
aircraft has been standing for 24 hours or longer, check that the
fuel has not become contaminated with water before flight. It is
generally preferable to keep tanks full whenever possible to
minimise water condensation the only exception being in hot weather
when there may be a risk of the fuel becoming heat soaked and
causing vapourisation problems see section 7 below. Only use fresh
supplies of fuel and after a period of protracted storage, drain
out any old fuel from the tank before filling up with fresh. Over a
long period of time the fuel in the tank will evaporate away the
more volatile fractions through the tank vents, leaving a residue
of low-volatility fuel which will cause poor starting, reduced
performance and possibly engine damage through detonation or
over-heating. When in storage, Mogas fuel has a much greater
tendency to form gum deposits than Avgas, so it has a much more
limited shelf life of just a few weeks. Avgas on the other hand can
be kept in sealed drums for several years. Gum deposits can block
carburettor jets and cause moving parts to stick. Even if your
engine appears to start and run well on last seasons fuel, you
should drain it off and replace with fresh. Mogas fuel is also
blended differently in the summer to that in the winter, to promote
easy starting and driveability. Using summer fuel in winter may
cause difficulty in starting, while using winter fuel in summer
will increase the likelihood of vapour problems (see section 7.
below) 1. In Use Except as described below, you should find no
difference in operation when you transfer from four-star to
unleaded, except perhaps a slight change in the colour of the grey
exhaust pipe deposits and less tendency toward plug fouling. 1.
Operating Limitations Unleaded Mogas fuel is restricted by CAP 747,
Appendix 8, General Concessions 4 and 5 to operation with a fuel
not exceeding 20 C and an altitude not exceeding 6000 ft. These
additional limitations must be displayed in the cockpit using a
suitable placard (see section 6 below).
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Special steps may be needed to prevent the fuel tank temperature
exceeding 20 C, especially during summer. Avoid letting the
aircraft heat soak in the sun for long periods before flight,
especially if the part containing the tank is painted a dark
colour. On a hot sunny day, avoid parking the fuelled-up aircraft
on dark tarmac surfaces. Consider instead filling the tank with
cold fuel shortly before take-off, or better still, leave in the
cool of morning rather than after a prolonged soak in the midday
sun. Assuming that your aircraft is cleared for use with both
unleaded Mogas and with Avgas 100LL, there is no problem with
mixing fuel of both types in your tank. Note however that even with
just a small proportion of Mogas in the tank, the vapour pressure
of the mixture will be almost as high as that of pure Mogas, so all
running on a mixture containing Mogas must be carried out observing
the operating limitations for unleaded Mogas alone. 1. Placards A
placard must be fitted alongside each fuel filler stating as
follows: UNLEADED MOGAS BS EN228, 95 RON A placard must be fitted
on the instrument panel, or other location in clear view of the
pilot in flight, stating:
USE OF UNLEADED MOGAS (see CAP 747, Appendix 8, General
Concessions 4 and 5) -only legal in aircraft specifically approved
for the purpose -fuel to be fresh, clean, water and alcohol free
-verify take-off power prior to committing to take-off -tank
temperature not above 20 C -fly below 6000 ft CARB ICING AND
VAPOUR-LOCK MORE LIKELY
Placards as above are available from LAA Engineering, free of
charge to LAA members. 1. What about Vapour Lock ? Unleaded Mogas,
like the obsolete four-star Mogas fuel, has a much higher vapour
pressure than 100LL or 80/87 Avgas. The initial boiling point of
the fuel is only slightly above ambient temperature, so it takes
only a slight raise in temperature or drop in pressure to make it
start to vapourise. This unfortunate property of Mogas makes it
much more likely to suffer vapour-lock or vapourisation problems
than Avgas, especially in hot weather or at high altitude. Hence
the limitations to 20 C and 6000 ft altitude which apply to Mogas
use, and the requirement to check that full engine power is
available before committing to a take-off. These special power
checks should not be rushed, as they also serve to burn off the
fuel which may have become
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pre-warmed in the fuel pump and gascolator while the engine has
been idling, and drawing fresh, cool fuel through from the tank
which will be less likely to cause vapour problems on take-off.
When the fuel turns to vapour in the fuel system, this can cause a
number of different problems and it is important for Mogas users to
understand the implications. If the vapour collects and forms a
large bubble which becomes entrapped at a high point or
constriction in the fuel pipe, this can form a vapour lock,
effectively preventing the passage of fuel to the engine and
causing a dead cut similar to what would happen if you were to turn
off the fuel cock. If this should occur, FLY THE AEROPLANE, lower
the nose, and if sufficient height is available in which to
experiment, turn on an auxiliary fuel pump if you are fortunate
enough to have one, and select another fuel tank. If the auxiliary
fuel pump is already on, you might try turning it off. If on the
other hand the fuel vapourises from some hot spot or low pressure
area in the fuel system but does not become entrapped, a stream of
vapour bubbles will enter the carburettor along with the fuel,
causing raised EGTs, lean running and reduced power, which in the
typical fixed pitch propeller installation is evidenced by a loss
in indicated rpm and possibly puffs of white smoke in the exhaust.
With Mogas, when carrying out the special power check prior to
committing to take off you should be looking and listening not only
for signs of uneven running but also an rpm which is less than
normal on the tachometer, either during the run-up or during the
initial stages of the take-off run. If either of these signs of
vapourisation occur, you MUST abandon the take-off as the symptoms
may well worsen as the engine heats up, and the power level may
fall away to nothing during the climb-out. If vapourisation is
suspected in flight, FLY THE AEROPLANE, lower the nose to maintain
airspeed, reduce the throttle setting so that the airflow into the
engine is reduced to correspond with the enfeebled fuel flow, and
richen the mixture control (if fitted) which should at least
restore the fuel mixture strength, smooth running and possibly
yield a few extra rpm. Since the symptoms may also resemble those
associated with carburettor icing, carburettor heat may be required
although this may have an adverse effect on fuel vapourisation
problems and you will need to experiment to identify the cause of
the problem before you can cure it. Vapour problems are most likely
to occur in aircraft fitted with engine-driven mechanical fuel
pumps, and are rarely experienced with a purely gravity-fed system
or those with an electric fuel pump situated at the tank outlet or,
better still, submerged in fuel within the tank itself as in modern
automotive practise. Unfortunately, in the typical aircraft system
the fuel pump is located above the fuel tank, so the fuel pressure
on the upstream side of the fuel pump is reduced below atmospheric
by the action of the pump sucking up the fuel, making it very
vulnerable to fuel vapour formation on the inlet side of the pump,
with symptoms as described above. If the engine is fitted with a
mechanical pump, bolted to the engine crankcase, then heat
conducted into the pump from the engine block will raise the
temperature of the pump body significantly and only the flow of
cool fuel through the pump keeps the pump temperature
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moderate. When the engine is shut down after a flight, the
cooling airflow through the engine compartment ceases along with
the flow of cool fuel through a mechanical engine-driven pump. As a
result the pump body temperature can rise alarmingly and
particularly when using the more volatile Mogas, you may hear the
fuel in the pump boiling. You may then notice the engine dripping
fuel from the intake drain onto the ground, due to the vapour
pressure of the boiling fuel pushing the contents of the carb float
chamber past the float valve and into the venturi. To cool the
engine compartment after shut-down it may help to open cowling
hatches and prop them open to promote convective airflow through
the engine compartment. Remember to latch them down before flight
though. If the fuel should vapourise within the fuel pump due to
elevated pump temperature, the fuel vapour generated inside the
pump body cannot escape back into the fuel system upstream, because
of the one-way valve on the intake side of the pump. So instead,
the vapour expands past the outlet valve of the mechanical pump, in
so doing pressurising the fuel in the fuel pipe and carburettor
float chamber, causing a so-called pneumatic lock. The vapour
pressure of the boiling fuel is enough to push the fuel past the
carburettor float valve and the engine suffers a rich cut, with
raised fuel pressure indications, rough running and characteristic
sporadic black puffs of exhaust smoke. The most likely time this
will occur is when the aircraft is flown, landed, parked for a
short time and then a second take-off is made. If this should occur
in flight, FLY THE AEROPLANE, lower the nose to maintain airspeed,
reduce the throttle setting to that appropriate to level flight and
attempt to restore smooth running by leaning the mixture. If your
aircraft has a mechanical pump with a back-up electric pump
connected in parallel, then it is important not to switch the
electric pump off too early after take-off, especially with Mogas,
as there is a risk that the fuel in the mechanical pump may have
been stagnant and vapourised away while running on the electric
pump, in which case the engine will stop as soon as the electric
pump is switched off. Fuel suppliers provide higher volatility fuel
in winter to help cold-starting. Be particularly wary of vapour
problems in spring and autumn months when winter fuel is being
supplied but ambient temperatures may be moderately high. A simple
piece of test equipment is available which allows the pilot to test
the volatility of his fuel and likelihood of vapour problems during
the pre-flight check. This is known as a Hodges volatility tester,
and is available at a modest price from Petersen Aviation Inc. in
the USA, tel. 001-308-832-2050. 1. Carburettor Icing The greater
volatility of Mogas compared to Avgas means that the carburettor
throat temperatures are lowered more by the atomisation of Mogas at
the jet than occurs with Avgas. Tests by the BGA showed that with
the same ambient conditions, the carb throat temperatures
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of a Lycoming 0-360 were typically 7 C lower with winter grade
Mogas than Avgas. The result is that when using Mogas, carburettor
icing will occur under higher ambient temperature conditions and
lower humidity than with Avgas. Take particular care to check the
efficiency of any carburettor heating provisions and to watch out
for signs of carburettor icing in flight. When using Mogas, use
carb heat more frequently and for a longer period than normal
especially on days when carburettor icing is likely refer to CAA
Safety Sense Leaflet on the subject. Carburettor ice remains a
frequent cause of engine failures, which suggest that fitting a
proprietary ice detector system to the carburettor may give a
useful safety benefit. 1. Chemical Compatibility During the daily
check and other routine inspections, pay particular attention to
non-metallic fuel pipes, fuel valves etc for signs of leaks due to
chemical attack from the fuel. There is a possibility that rubber
pipes, seals, gaskets, O-rings, fuel tank sloshing sealants and
even the varnish on cork fuel gauge floats may be affected by
constituents within unleaded fuel. Standard MS29513 aviation
O-rings swell significantly in size when in contact with unleaded
Mogas, which may affect the operation of fuel valves, gascolators,
fuel filler cap seals etc. All these points should be borne in mind
during your pre-flight checks. You should also check filters
frequently for signs of contamination either from the fuel or
resulting from chemical attack on fuel system components or the
fuel tank. Viton rubber is unaffected by unleaded fuel. O-rings of
Viton rubber are available from specialist seal suppliers. 1.
Continental and Lycoming Engines With these engines, many of which
were originally produced many decades ago, there have been a
variety of different valve seat and valve materials used over the
years, and there is a possibility that some combinations in the
field might suffer problems with valve seat recession if deprived
of the dry-lubricating effect of tetraethyl lead in leaded fuels.
To guard against this possibility it is recommended that all users
of Continental and Lycoming engines cleared for unleaded Mogas use
should either use a fuel mixture with 10% 100LL in it or run a
tankful of 100LL through the engine at least every 75 running hours
to lubricate the valves and valve seats. If you have the engine top
overhauled or majored, it is recommended that you run the engine on
100LL Avgas for the first 10 hours operation afterward to ensure
adequate lead content during the break-in period. Due to the
likelihood of 100LL being withdrawn in the not too distant future
for environmental reasons, it is recommended that when Continental
or Lycoming engines come to be
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overhauled, the cylinder assemblies are replaced with new
assemblies known to be compatible with unleaded fuel, which will
not require this occasional doping with leaded fuel. Some
Marvel-Schebler (latterly, Facet and now Precision Airmotive)
carburettors may still be fitted with moulded cellular rubber
floats, as introduced by FAA AD 66-05-04 (withdrawn in 1985). Some
of these floats have given trouble due to soaking up fuel, loosing
buoyancy and dropping in level, causing rich running problems, i.e.
flooding carburettor, rough running at idle speed and inconsistent
shutdown. Facet Service Bulletin A1-84 refers. While the composite
floats are no more likely to absorb unleaded Mogas than they are
100LL fuel, owners should be wary of this problem and if problems
are experienced, consider fitting a replacement float (Precision
Airmotive Service Information Letter SIL MS-4). Some Bendix NAS-3
carburettors may still be fitted with obsolete synthetic
rubber-tipped needle valves, which should have been replaced with a
Delrin-tipped needle under Bendix Aircraft Carburettor Service
Bulletin ACSB-84. While Bendix advise that their own original
neoprene-tipped valves should not cause any trouble if used with
unleaded Mogas fuel (and this seems to be confirmed by the LAAs
submersion tests) a problem has been reported in the USA with bogus
neoprene tipped valves which swelled up when submerged in fuel and
caused excessively lean engine running. The bogus valve tips
respond equally when submerged in 100LL fuel. Nevertheless, owners
should be aware of this potential problem if they suspect that the
neoprene-tipped valves are still fitted. 1. Rotax 912, 912S and 914
Engines The Rotax 912, 912S and 914 engines have been designed to
run on unleaded Mogas however a vapour return line must be fitted
to the fuel system in accordance with Rotax recommendations. If the
aircraft is not already fitted with one of these, one must be
fitted to a scheme acceptable to LAA Engineering. 1. Rotax 2 Stroke
Engines Rotax 2 stroke engines are designed to use unleaded fuel
and you should find no difference in operation when you transfer
from four-star to unleaded, except perhaps a slight change in the
colour of the grey exhaust pipe deposits and less tendency toward
plug fouling. Unleaded Mogas, like four-star fuel, has a much
higher vapour pressure than 100LL Avgas. Consequently it is much
more likely to suffer vapour-lock problems causing engine power
failure, especially in hot weather and high altitude. Hence the
limitations to 20 degrees C and 6000 ft altitude which apply to
Mogas use, and the requirement to check that full engine power is
available before committing to a take-off.
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Fuel suppliers provide higher volatility fuel in winter to help
cold-starting. Be particularly wary of vapour lock in the autumn
months when winter fuel is being supplied but ambient temperatures
are still high if we are lucky enough to enjoy an Indian summer.
Engines running on unleaded Mogas fuel are more likely to suffer
carburettor icing than when running on 100LL. Take particular care
to check the efficiency of any carburettor heating provisions and
to watch out for signs of carburettor icing in flight. During the
daily check and other routine inspections, pay particular attention
to non-metallic fuel pipes, fuel valves etc for signs of leaks due
to chemical attack from the fuel. Check filters frequently for
signs of contamination either from the fuel or resulting from
chemical attack on fuel system components or the fuel tank. 1.
Jabiru Engines Jabiru warn that although their engines may be
operated on 95 UL Mogas provided the compression ratio is not more
than 8.3, there is nevertheless an increased risk of detonation
when unleaded is used rather than 100LL Mogas. An installation
which is marginal with regard to cylinder head cooling may suffer
problems with detonation and engine damage when transferred to
Mogas fuel. Be particularly wary of any signs of detonation, warped
or leaking heads which may be a sign of detonation occurring which,
if left unchecked, are likely to result in major engine damage and
in-flight engine failure. 1. VW and VW based Engines VW and VW
based engines are suitable for 95 UL Mogas use, provided that the
engines compression ratio does not exceed 8.0:1 although there is
the possibility that engines not fitted with hardened valve seats
may suffer from rapid valve seat recession if deprived of the
dry-lubricating effect of tetraethyl lead in leaded fuels. To guard
against this possibility it is recommended that all users of VW and
VW based engines cleared for unleaded Mogas use should either use a
fuel mixture with 10% 100LL in it or run a tankful of 100LL through
the engine at least every 10 tankfuls to lubricate the valves and
valve seats. Checking the compressions by turning the propeller by
hand should give an indication if valve seat recession has become
excessive, but the valve clearances must be measured at least once
every 25 hours and adjusted if the clearance is found to be on or
out of limit. Excessive exhaust valve clearance will introduce the
possibility of valve burning which may lead to engine failure. If
you have the engine top overhauled or majored, it is recommended
that you run the engine on 100LL Avgas for the first 10 hours of
operation afterward to ensure adequate lead content during the
break-in period. Due to the likelihood of 100LL being withdrawn in
the not too distant future for environmental reasons, it is
recommended that when VW and VW based engines come to be
overhauled, the
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cylinder assemblies are replaced with new assemblies known to be
compatible with unleaded fuel, which will not require this
occasional doping with leaded fuel. 1. If Problems Occur While the
foregoing is based on the best information available at the time,
ultimately Mogas supply is not as tightly controlled as Avgas and
there is therefore more scope for problems of contamination or
mis-identity. No guarantee can be given that fuel is of the type
specified on the pump, and only by constant vigilance can safety
standards be maintained. Remember that the CAA continues to take
the view that engine failure is always a possibility in
single-engined aircraft. Consequently the pilot has a duty to
operate it in such a way that engine failure would not case a
hazard either to himself, his passengers or third parties on the
ground. If engine problems occur which appear to relate to fuel
type or fuel contamination, contact the CAA as described in the
Airworthiness Notices along with copies of the appropriate fuel
receipts. 1. Further Information Much further information about the
use of unleaded Mogas is available from the websites of
Petersen Aviation (www.webworksltd.com/webpub/PetersenAviation)
and the EAA
(www.eaa.org).
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Appendix C
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The original online document is located at:
http://web-dev2.shell.com/global/products-services/solutions-for-
businesses/aviation/aeroshell/knowledge-centre/technical-talk/the-blue/issue-6-2007.html
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Appendix D
Re: Mogas as used by Flybest Flight Academy When we first
started flying the planes here in Batam, we were using Avgas. We
found generally, that the planes performed very well, delivering
very close to book performance figures. There was never a chronic
problem with plug fouling. Only rarely did we have to clear plugs
after startup. And at no time was it severe enough that the
mechanics needed to pull plugs to clean them. After the switch to
Mogas, we all noticed an oily feel to it. I once remarked to the
Chief Flight Instructor that it smelled familiar, but couldn't
think what the small was, maybe like paint thinner, or toluene .
Within the first week, I found I had to clear the plugs after EVERY
startup. I began to wonder if this mogas was the same as the mogas
in the USA or England. Also, I found we had more contaminants in
the fuel whenever we checked the tank contents as required before
every flight. Eventually, I was forced to cancel flights because
even the plug clearing procedure would no longer get the engine to
run smoothly. The mechanics had to manually clean the plugs. I
suspect every day. Eventually, this caused us to lose the use of
one aircraft, due to repeated removal of the plugs from the engine
to clean. Resulting in Murphy's Law reaching out to us... one of
the cylinders was found with damaged threads in the spark plug
hole, taking a long time for the parts for the repair to reach us,
grounding the aircraft. I also started to see what looked like an
oily yellow liquid in the fuel samples taken during preflight,
forcing us to drain up to half liter of fuel sometimes to get clean
fuel from each fuel testing point. Every single engine start, began
to require plug clearing in order to run smoothly... And more than
once only to run poorly before take-off and force us to cancel
another flight while the technicians did their drill....i.e. pull
and clean plugs manually. After a while, I noticed the engines
starting to not run as smoothly as they used to, occasionally
giving little hick-ups while in cruise and other configurations. I
guessed at the time it may have been a little water that escaped
sumping. When reported to the mechanics, they checked what they
could, found nothing wrong and returned aircraft back to service. I
fully expect that if we return to mogas, we will definitely lose
another aircraft. And this time, we may not be so lucky.
Raymond Duquesnay
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Appendix E
From: Stefano Marras Flight Instructor Date 8 December 2013 To:
Denis Boissonneault, Chief Flight Instructor Sunject: Mogas Report
Following the request from the Chief Flight Instructor of the
Flybest Flight Academy regarding my personal opinion about the
quality of the Mogas fuel used during the flight operations I'll
state as follow: Since the very first day of the usage of the Mogas
in the airplane I personally noticed and notified to the Chief the
unusual properties of the fuel. Especially when we were draining
the fuel I noticed it was unusually oily and greasy and most of the
time it was contaminated with bubbles of a yellow oily substance.
Sometimes was necessary to drain the fuel several times in order to
eliminate entirely the problem before the flight. After the
completion of the draining operations the fuel strainer was most of
the time unusually oily: little oily bubbles were present all
around the inner part of the strainer causing my concerns
(discussed several times with my colleagues) because those bubbles
were very persistent to be removed so very likely the same was
happening inside the cylinders with potential unsafe outcomes... At
the same time of the usage of the mogas I started to notice a
change in performance of all the airplanes and, as reported on the
journey log, I begun to experience problems during the starting
operations, engine run-up operations and magneto checks. They were
unusual especially considering how often those kind of problems
were rising. After few days from the first flight with the mogas,
as reported on the journey log, I experienced a significant loss of
power of the engine immediately after takeoff with KFA but the same
type of problems showed up later with the same characteristic few
weeks later with all the other airplanes with a tendency to get
worse. Concluding I like to highlight the fact that in my previous
experiences (where I was flying always with Avgas either in Italy
and /or in the US) I never experienced similar problems with any
airplane that I flew. Stefano Marras
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Appendix F
From: Lidia Roset Soler Flight Instructor Date 8 December
2013
To: Denis Boissonneault, Chief Flight Instructor Sunject: Mogas
Report
As I said in September in DGCA meeting, I flew in Greece for
almost two years using MOGAS in Cessna
and Pipers airplanes. During all this time in Greece I never had
any problem with fuel or airplanes.
The MOGAS used in Greece, was yellow and the smell and the
feeling was completely different that the
one in Batam. The Greek company bought every day fresh.
0 MOGAS in a little gas station close to the airport.
The weather in Greece is different than in Batam. Greece has
four seasons, during winter and fall the
temperatures are very low, but during spring and summer time the
temperatures are very high. In
Thessaloniki around 40 degrees Celsius and the humidity 90 per
cent
The first thing that I notice when I came to Batam is the
difference between the MOGAS used in Greece
and in Indonesia, not only in the color, smell and texture, as
well in the problems that we have in all the
starts, cleaning plugs over and over again
I hope my previous experience with the MOGAS help to clarify
things
Lidia Roset Soler
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Appendix G
MOGAS Use.docx
Karin, 25 October, 2013
I thought much about our discussion with regards to the 3
packets of information about the
MOGAS that I gave to you on Tuesday 22 October. Considering that
the fuel was received in
June and can only be stored only a few weeks before it goes bad
I cannot allow the MOGAS we
have in stock to be used in the aircraft no matter what we mix
it with. There will be no way to
guarantee the safety of flight with such fuel in the aircraft.
The reports I showed you give every
indication we have seen in our aircraft since we first started
using the fuel in June.
PK-KFA:
On June9, June 10, June 11 and 12 the aircraft was squawked for
loss of power. The cause of
the loss of power was the sparkplugs had deposits on them and
needed to be cleaned. On 12
June the aircraft also had high oil temperatures.
On August 1 the aircraft was grounded for high oil temperatures
and we removed and replaced
the Oil Cooler as we thought that may be the issue. PK-KFA
continued to have high oil
temperatures after the new oil cooler was installed.
PK-KFB
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On 30 August the aircraft was squawked for a rough running
engine and the plugs were
cleaned.
On 11 September the aircraft was squawked for rough engine and
the spark plugs were
removed and cleaned.
PF-KFC
On 7 September the aircraft was grounded for loss of power and
the Sparkplugs were cleaned.
On 11 September the aircraft was squawked for loss of 200 RPM
during the run up.
Maintenance replaced 2 sparkplugs and cleaned the others due to
deposits on the sparkplugs.
On 12 September PK-KFC went down due to engine failure which was
caused by detonation.
With regards to the accident of PK-KFC and the question of
leaning procedures, the density
altitude the time of the accident was 1700 feet. When the engine
experienced the detonation
it was at 1500 feet AGL which would have put the aircraft at a
density altitude of 3200 feet.
Lycoming recommends leaning the engine above 3000 feet. During
the investigation by the
insurance company the investigator noticed that there was no
scoring or scratches on the
inside of the number 2 cylinder which was caused due to the fact
that the engine stopped
running instantly after the detonation happened and did not
happen during the climb or over a
long period of time. The loss of power was reported the day
before as noted above. In the
report from the Light Aircraft Association it states If on the
other hand the fuel vapourises from
some hot spot or low pressure area in the fuel system but does
not become entrapped, a stream
of vapour bubbles will enter the carburettor along with the
fuel, causing raised EGTs, lean
running and reduced power, which in the typical fixed pitch
propeller installation is evidenced by
a loss in indicated rpm and possibly puffs of white smoke in the
exhaust. The procedure of
leaning of the engine was not the issue of the detonation or
engine failure of the engine. The
procedure of leaning the engine has been in place since the
school started operating in January
and none of these symptoms began until June when we began using
the MOGAS.
PK-KFF
On 28 July PK-KFF was grounded for right magneto dropping to
many RPM during the run up
prior to take off. The mechanics replaced 4 spark plugs due to
residue on them.
Synopsis
Every aircraft was noted to have a reduction in performance
later as the fuel was continued to
be used. All the pilots and maintenance noticed the fuel was
sticky and had a funny smell to it
when we first started using the MOGAS fuel from the first day of
use.
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Maintenance said that when the MOGAS fuel drums arrived they had
corrosion and looked very
old and faded.
Since we started using the MOGAS we have replaced a total of 12
Sparkplugs due to deposits
on the sparkplugs.
All of the symptoms stated above are from old fuel and started
when we started using the
MOGAS we have in stock. All the squawks are from the aircraft
journey logbooks and Flight
Schedule Pro maintenance discrepancies. Every symptom associated
with old fuel is present in
the historical data of the aircraft and it all started in June
through September using both mixed
MOGAS/AVGAS and straight MOGAS. The mixing of AVGAS into the
fuel we have now cannot
be done as we cannot prove that it will make the fuel safe for
use. According to the
information we have this practice will not fix the issue as the
report from the Light Aircraft
Association states Assuming that your aircraft is cleared for
use with both unleaded Mogas and
with Avgas 100LL, there is no problem with mixing fuel of both
types in your tank. Note
however that even with just a small proportion of Mogas in the
tank, the vapour pressure of the
mixture will be almost as high as that of pure Mogas, so all
running on a mixture containing
Mogas must be carried out observing the operating limitations
for unleaded Mogas alone.
Prior to the use of the MOGAS we had no indication of abnormal
engine operations. There
were several other instances where the maintenance was alerted
to a rough running engine
and they cleaned the sparkplugs after the use of the MOGAS
began. Almost every flight we had
to clear the magnetos due to a rough running engine to remove
deposits from the sparkplugs.
When I asked you how long it took for fuel to arrive from the
time it was ordered you said it
takes about a week. If you want to test the fuel and the results
take another week that will put
the use of fuel to only one week until we have to dispose of it
due to the end of its shelf life of 2
to 3 weeks. I cannot verify the date of manufacture of the fuel
we have received so far.
When I asked the maintenance engineers why we kept using the
fuel when it was thought to be
the cause of these issues I was told that they had notified you
several times about the fuel
being an issue and they were told it was too expensive to use
AVGAS and that if they wished to
use such fuel someone else would have to pay for it.
Since we have switched back to pure AVGAS we have had only one
issue of power loss from an
aircraft and that was during flight when power was reduced below
2000 RPM during a day with
very high humidity which caused the carburetor to develop
carburetor icing. No student pilots
or instructors have had to clear the magnetos to burn any
deposits off the spark plugs since we
have changed to pure AVGAS.
Conclusion
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With this knowledge and the research I have given to you by
Light Aircraft Aviation group *1
and Shell Oil Company *2 and the Civil Aviation Authority of the
UK *3 stating that the fuel
should not be used above 20C due to the volatility being higher,
and the chance of vapor lock
happening as well as carburetor icing, the symptoms of old fuel,
and the fact that the fuel we
have in stock was received in June, we cannot use of the MOGAS
we have in stock and a
different solution needs to be found.
The argument of financial savings for the company using MOGAS
instead of using AVGAS
weighs heavily towards AVGAS. During the months of January until
we started using the
MOGAS we never had an aircraft down or squawked for engine
issues. Since we have started
using MOGAS and a mix of AVGAS and MOGAS we have lost a total of
99 flying days due to
aircraft on the ground. That is a loss of around 400 flight
hours. The cost of 12 sparkplugs of
$29.83 each or, a total of around $358 and around 400 man hours
due to the use of the MOGAS
and the loss of an aircraft reducing our fleet by 20% is not
efficient and is actually very
expensive.
As the Chief Flight Instructor here at Flybest Flight Academy I
cannot allow the use of MOGAS
fuel in our aircraft since it is an obvious risk to the safety
of our students and instructors. The
fuel MOGAS may be usable to other climates with cooler
temperatures and faster delivery
times but it cannot be done so here.
I hope you can understand why I have taken this position with
regards to the use of the MOGAS fuel. I have the responsibility to
the students, staff and company to prevent anything that has to do
with safety from affecting the outcome of any flight or training
the students will receive here at FlyBest. I do understand the
concept of saving costs and being as efficient as possible.
Sincerely, Denis R. Boissonneault Chief Flight Instructor FlyBest
Flight Academy
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Appendix H