Loss of power during take off

[Slow_Poke]

Hi guys, please help! Yesterday afternoon i took of after all the necesarry check, mag checks ok every thing seemed fine until i reached +/-400ft agl, engine started to loose power and spluttered a bit, could only get 3000rpm max, luckily not to far from runway, put her down safely and trying to figure out what happened? I changed from castrol super outboard 2stroke to super chainsaw 2stroke and unleaded petrol after speaking to Niren at aviation-engines (flushed the whole system and started with fresh petrol and oil - didnt want to mix the different types of oil), checked the plugs and they were 100% - please help!

[Morph]

Sounds like fuel starvation,

did you check you fuel filter? did the plane start fine again on the ground,

Check the whole fuel system, for dirt, blocked fuel filter, water in the tank, cracks in the fuel pipe, vacuum pipe etc.

Do you have an inline standby electric fuel pump installed, if not look at getting this done asap, it's cheap and will save your bacon in a case like this. See this thread http://microlighters.co.za/viewtopic.ph ... +fuel+pump

I changed from Super outboard to Super Chainsaw 100 hours ago on the 503 and I have had no problems at all.

You should not get gelling by mixing the two types of fuels, they are both mineral and I have flown with a mix of both in my tank when I cannot get the one, I have used a bottle of the other to get by.

[Cloud Warrior]

Not to be alarmist but this happened to me during my training. Lost power on take off and landed straight back onto the runway - (thanks for the good training Johann!). Did some run ups on the ground and everything seemed fine. Flew for half an hour and put the plane away. Next day another student went up and landed in the veld near Langebaan with a hole in the piston head. Rings were gone on the one cylinder. I was amazed that the 503 kept flying for so long after things started going wrong.

I would give everything a really good once over before flying again.

[Duck Rogers]

Stephan, how long did you have the engine idling before you took off? And, importantly, as Morpheus asked, did it start up again after you landed and did it get full revs again?

Check the whole fuel system, for dirt, blocked fuel filter, water in the tank, cracks in the fuel pipe, vacuum pipe etc.

You may have dislodged some dirt, twisted a pipe, nicked a pipe etc.etc. during the time you flushed the system.

Duck Rogers

[Slow_Poke]

started fine on the ground, did a full power check, got max rpm and after +/- 30 seconds, same thing happened. Glen at microflight sugested that it might be one of the carb's float level not being right - might be getting in to much or to little fuel in the boal? the CHT was also a bit lower on one of the cylinders (20deg or so) could that indicate something?

[Slow_Poke]

engine was idling for +/- 10 minutes while waiting for a blik aerie on finals

[Morph]

I have usually found that if a problem arises go back to what you have recently touched or moved etc. For example you have been working with the fuel system and have probably introduced a fuel system problem to the plane. The float level problem won't suddenly introduce itself.

Part of your full fuel system check will be to check the float chambers. Start it and wam it up, then run the motor up until it starts failing, shut off immediately and check the fuel level. Just remember if there is a fuel starvation problem, i.e. blocked filters, cracked pipes etc the float level will be low or even dry.

[Morph]

My CHT's are very rarely identical. In fact I find the front one always coller than the back. Might be airflow etc. As long as the EGT's are within 25deg of each other your carbs are well balanced.

[salem]

Hi Stephan

Please refer to Rotax Service Information circular number 4UL87-E of May 1990 which you can download from the net. It refers to several possible solutions to a) sudden rpm drop, or b) engine stops during flight while it operates again on ground without troubles. To summarize:

1. Check that prop and prop-drive are correctly matched to engine.
Engine must reach its nominal rpm
2. Fuel pressure must be between 0.2 and 0.5 bar (3 to 7 psi) measured
between fuel pump and carb.
3. Check for water in the carb.
4. Ensure that the fuel pump is not fitted too rigidly on the engine to avoid
excessive heat and vibration.
5. Check that fuel is not foaming in float chamber. Possible causes for
this are: a) unballanced prop
b) inadeqate engine suspension (excessive vibration)
c) spring damping of float needle valve not appropriate for
vibration conditions. This could happen at only a certain
rpm range
6. Check float needle valve for:
a) tip of needle valve resp. tightness of valve
b) float level
7) Check intake system between carb and engine for leaks (rubber flange
and intake socket)
Check ignition system:
a) ignition timing (refer to manual)
b) spark plugs
c) break-away gap
d) ignition coil (interchange magneto side with pto side)
e) mass cable and mass contact. Bad mass contact may cause piston
seizing or hole in piston
f) ignition cables (check for pin holes)
g) spark plug cover damage. Ensure that isolation of the resistor spark
plug cover is not disrupted
h) ignition damping box (refer to manual)

I hope that the above may be of some help

[Griffin]

5. Check that fuel is not foaming in float chamber.:

How do you know if the fuel is foaming??

Check ignition system:
...
c) break-away gap
..
e) mass cable and mass contact. Bad mass contact may cause piston
seizing or hole in piston
. ..
h) ignition damping box (refer to manual)

What are these? Is this only applicable to an engine with point?

[Duck Rogers]

engine was idling for +/- 10 minutes while waiting for a blik aerie on finals

All the classic symptoms of a Cold Seizure
What was the OAT "outside air temperature"?
Pull the exhaust manifold and check the pistons and sleeves.

Exactly as Cloud Warrior's experience

Duck Rogers

Edit added: Check for vertical scuff lines on the pistons. These can easily be seen through the exhaust port with the manifold removed.
DO NOT BE TEMPTED TO FLY THE AERRIE EVEN IF IT DEVELOPS FULL RPM!
Find the fault first...it's cheap insurance to check the pistons rather than expensive airframe repairs...you might not be lucky a second time around with a suitable landing area

[Slow_Poke]

OAT - 15 deg's. I stipped everything this weekend - everything 'A Ok", but found the problem - dirty aircleaners - took them off, started and did full power check for a few seconds - repeatedly and then swopped the air cleaners with another trike's and what do you know!!! Could it really be this simple??

I changed everything, including fuel lines, filters, plugs, drained fuel and filtered it checked pistons - no coloration / scuffmarks and EGT & CHT Temp normal.

[Morph]

The real test would have been to install the airfilter on the other trike, start it and see if it develops the problem.

[C205]

Had similar experience on a 503 during solo training. Engine ran fine until I needed a bit of extra revs (on take-off etc). Was 100% in cruise. Did a touch n go at FAWI and felt like I was going nowhere. Started spluttering on downwind again. Did an abbreviated circuit and put it down again. No problem during taxi etc or when engine was cold. Phoned instructor to collect the trike. I was beginning to think I am paranoid and imagining it all but instructor had same problem on flight back to his strip.
Turned out to be fuel filter problem.

[Slow_Poke]

will be testing air filters on a nother trike this afternoon - will let you know what happens