Tecnam carb icing
 

The P2006T I have been flying suffers from carb icing almost every morning during taxi and frequently during flight.

Last week during taxi one engine stopped (I didn’t put the heat on in time) and within 5 minutes whilst at the hold point I saw another Tecnam with a stopped engine. Only this one was on the runway and had been given a clearance for takeoff causing a go around for the final traffic.

Has anybody had a similar experience with the Rotax 912, or more specifically the Tecnam?

Given the time of year I am very conscious of losing an engine in IMC.

Never had carb icing in around 1500 hours behind Rotax 912 and 912S engines. And have not even had a carb heat system in last few hundred hours. However, the air filters have always been at he back of the cowled engine compartment so the intake air gets quite warm quite quickly.

In the Tecnam, is cold air ducted in from outside? If so, think you will need an effective carb heat system.

I've maintained and ground run a number of P2006Ts for 7 years or so.

On cold damp mornings in particular, the engines do ice up but clear quickly with the use of carb heat (even with a cold engine). Once the engines are warmed up to operating temp (oil temp 50°C) then they're fine and don't tend to ice up. I've never heard anyone reporting issues in flight be it during training, cruise, IMC or whatever.

I always taxy them with carb heat on 'hot' on cold, damp mornings.

Carb heat is provided from hot air ducted from a shroud over the muffler (like Lycomings) feeding the single air box that is normally used on the certified 912S.

Easy to fit on a permit aircraft but not so sure on the Techam P2006T, But a small water heated manifold between the carburettor and inlet manifold is all you need, Used to be sold by Skydrive in the UK but sure they are available elsewhere if you look,

Unfortunately the Skydrive coolant heated carbs mod isn’t certified so can’t be fitted to any certified aircraft like the P2006T.

Works a treat - we have it on our own 912ULS in a Permit to Fly machine. Carbs are kept ‘warm’ by the coolant so ice never forms. No loss of power because the induction air is always cool.

Which make a mockery of of certified regulations, Just finish reading an AAIB report on a Techam P2006T in Latvia, two fatal with a strong possibility of carb icing being one of the reasons for the Accident,

I never really understood why "certified" actually means "expensive and not up to date"... I would have thought that in this day and age, certification would be cheap and fast! (or at least it should be...)

can you pass on a link to that report? The one I'm aware of was a crash in exam conditions where examiner cut of fuel for one engine but the student feathered the other engine and stalled the aircraft

This is what you are looking for.


http://www.taiib.gov.lv/uploads/Final%20Report%20%20Bukultix%200.pdf

page 64 is the relevant bit i was referring too,

Some 55 years ago I learned the basics on an Aircoupe with Continental C90. From the outset students were instructed to use carb heat at all times except for takeoff and initial climb. When the throttle came back, so did the carb heat knob. The instruction followed several frights caused in all seasons, culminating in a well executed forced landing from which the aircraft was flown out. I never encountered another aircraft so prone to carb icing, it certainly was not as bad in the Piper Cub C90 installation.

As a licensed engineer I was able to monitor the Aircoupes for many years. The engines were unaffected by the procedure and remained very reliable until the a/c reached end of service. I know not the first thing about the machinery mentioned, but sometimes old remedies still work.

Just to keep things in perspective, the P2006T does not in my experience (maintenance of and being involved with operations of many of the type over a number of years) suffer from carb icing in flight in/above the UK. They only seem to suffer from it when the engines are cold, pre-flight. For those that don't know, power checks are not carried out on a Rotax 912S until the oil temp has reached 50°C by which time carb icing does not seem to be an issue.

You certainly do not want to be operating a P2006T with the carb heat on hot all of the time, it won't like that as the carb heat system does work well when in hot and as with most aircraft engines, there is a drop in rpm when it is selected.

Not that I have ever sat in a P2006T or flown behind a 912is but I cantcseecfor the life of me why they don't mate the airframe with the fuel injected engine.

smart hawks
Interesting to hear the consensus that it does not suffer icing in flight, which is not what I think I have experienced.

I have noticed the the temp does drop significantly after I reduce power to 19 or 20, so I tend to leave the carb heat on particularly if there is moisture in the air.

Other than the drop in rpm which I can compensate, what other negative effects are there on the 912 caused by leaving the heat on?

My comments about the P2006T were attempting to allay your fears that an engine might suddenly run down without warning in flight (‘IMC’) as you have experienced when taxying with cold engines, especially when the air is cold and damp.

I was taking it for granted that you perform standard FREDA checks and give the engines a blast of carb heat regularly. If you’re operating at low power (descending or perhaps aerial survey/photo work…) then the risk of suffering carb ice is greater, as with most carburetted aircraft piston engines.


The P2006T Aircraft Flight Manual dictates that carb heat should be used ‘as needed’ in cruise (Section 4 Para 3.10).

In the AFM Section3 Para 5.5 (carburettor icing), it expands on this as follows (remember that the P2006T is not approved for flight into known icing):

‘5.5 CARBURETTOR ICING

DURING TAKEOFF

The carburettor icing in “full throttle” mode is unlikely.
Take off in known or suspected icing formation is forbidden; in order to dispose
of full engine take off power, take-off must be performed with carburettor heating
OFF.

IN FLIGHT

Carburettor icing is considered probable when external air temperature is below
15° C and visible air moisture (clouds, mist, haze or fog) or atmospheric precipitation
are present.

Generally, an OAT-to-dew point temperature spread lower than 10°C and OAT
less than 15°C with visibility lower than 5 km is a positive indication of likely icing
formation condition.

Should an inadvertent flight into known or forecast icing condition happen carburettor
heating should be selected “ON” as soon as possible: the greater the advance
carburettors are warmed the better the chances not to form ice and avoid
engine power loss or reduction.

Keep Carb Heating “ON” until engine power is restored and area of possible icing
condition is exited.

CAUTION

Carburettor Heating selected to “ON” will cause engine RPM reduction
of about 100 RPM causing a sensible available engine
power decrease.’


My comment about not running with carb heat selected to ‘on’ all the time is based on the fact that the engine will be running richer, which is not ideal for it. The carb heat system is effective (ie the air it feeds is hot) so there is a substantial drop in rpm when compared to some installations like the Chipmunk Gipsy Major which in military use were normally locked in ‘hot’).

Many non-certified Rotax installations don’t have any carb heat at all but are fed through individual air filters, taking their air from within the engine bay where is warmer than ambient. Personally when building our Permit aircraft, we wanted to reduce the risks of carb ice as much as possible and liked the Skydrive system for its relative simplicity, so fitted that.

I would suggest that you might contact the former UK Tecnam dealer as his operational experience with the aircraft (and as one of the most experienced instructor/examiners in the UK) is probably the best advice you can get.

Contact details here: https://www.avbuyer.com/dealers/details/tecnam-uk#

Reference the 912iS – it isn’t exactly a simple swap and yes, it does get rid of any carb ice issues but there are cost and weight penalties involved for no extra power (possibly better fuel consumption). A 915iS might be a good step up when it is available as at least there is more power to offset the negatives.

Did my IR on the P20006T in Poland in January / February with plenty of time spent IMC - never had an issue with carb ice, just followed "standard" carb heat procedures (carb heat on when power reduced etc).