Use of Carb Heat

[1279shp]

Here's an interesting one for all.

Use of carb heat during 'stall' training.

Does it matter carb heat OFF before recovery or after?

Recover + Power + Carb Heat
Recover + Carb Heat + Power

Realising training is @ FL030

@@

Also in a go-round situation during training, shud it be firewall throttle then/as carb heat OFF, or carb heat OFF then/as firewalling throttle.

Your thoughts/training/methods?
:hmm:

[Massey058]

Massey teach carb heat off at 60 KIAS when doing stalling training (in the PA28). I don't recall a specific action in regard to the carb heat in the go-around if but if I was anticipating it I would go for carb heat off before applying power.

[mattyj]

If your hand is big enough you should be able to do everything at once..Mixture/pitch/power/carb heat..make your checks easier..in reality all the schools are teaching carbheat off at some point prior to full power to obtain best power when required.

Still leaves the Carb vulnerable at the moment it is most susceptable to icing..idle power!:hmm:

[cjam]

The skool I was at taught turning the carb heat off on finals and opening the cowl flaps at the same time. I don't feel particularly strongly that its the best thing to do but once you're in the habit it worked. I suppose it depends on how quickly the icing is likely to occur as to weather that is a good technique or not.

[LocoDriver]

Aero clubs and schools teach carb heat off at around 60kts approaching the stall.

On approach, carb heat should be on, until finals, when you are within GLIDE distance of the runway. IE, crossing the fence.

Carb heat is to be used.

Cheers!
:ok:

[1McLay]

hmmm, think I just got deja vu

:confused: :confused: :confused:

[The Messiah]

In the stall recovery if you do the carby heat after advancing the throttle the delay in achieving full power would barely be noticeable and would not increase height loss at all, as a recovery with power is always recovery with minimum height loss is it not?

As for every approach with carby heat on? I cannot agree with that. Carby heat is to be used as required. I don't think that it would be required at all for 99.99% of flights and is one of those items students can start to learn judgement with, which is a very difficult to teach but very important quality in any pilot.

[Aerodynamisist]

I don't know if there is a standard method for carby heat I was tought to use it all the time when below 1800 rpm on approach stalls forced landing practice ect.

However I teach the use of carby heat when any one of these three conditions exist
* visible moisture * high humidity * low air temp < 20 c .
Always go for the power first - maintain control - and put the carb heat in first on the list for cleaning up the aircraft.

It won't hurt to use carby heat doing stalls but I wouldn't stress about getting it in quickly in the recovery phase.

Ive never opened up the cowl flaps on finals and always keep em closed. The donks arn't going to heat up that quick in a go around if any thing they may be too cold and a slow advance of the throttle may be needed so you don't blow a pot (hot piston expanding in a cold cylinder causes excessive wear and can be as bad as shock cooling).

It's not enough to just shift the levers to a procedure you have to know the theory behind and what problems your trying to over come to develop a system for managing your aircraft.

[Dupre]

It makes no difference whether you practice your stalls at FL600 or 600'. The object of the exercise is to recover with minimum altitude loss, so that if you ever get too low & slow causing a stall at 100', you've got the best chance of survival.

To do this, you want to get as much power as you can, as soon as you can.

2 Scenario's:

(1) Stall -> Carb Heat Off -> Full Power
<Low Power> <Low Power> <High Power>

(2) Stall -> Full Power -> Carb Heat Off
<Low Power> <High-ish Power> <High Power>


The second of these gives the aircraft more energy over the same time, so gives a lower altitude loss.

From FL030 it doesn't matter a jot, but from 100' it could mean life or death.

I treat go-arounds the same, though as you remain in controlled flight the whole way, it is not quite as critical...

Just my 2c...

Dupre.

ps After writing all the above I realised that I had forgotten to mention that all through my stall training, carb heat was turned off before the stall - meaning that I didn't have to think about it for the recovery.

When on approach (the most common low & slow scenario) carb heat is likely to be on, so I would argue that training should reflect this, by not turning carb heat off until after the stall.

[The Messiah]

Yes Dupre, I agree with you and surely the first reaction to teach a student encountering a stall must be, 'full power'.

Bugger the carby heat!

[Centaurus]

From the manufacturer's POH. Don't forget that if the carb heat is on during final approach (as it should be according to Cessna 172N and 152), you leave it on until after landing. If you conduct a go-around, apply full throttle and only then do you follow up with carb heat cold. (allows warm air in to ensure ice has a better chance of melting).

As a touch and go is just a go-around on the runway same principle. - that is full throttle then carb heat cold. This is type specific but the reasoning make sense.

[jimmydacraw]

I always follow the POH.

As an aside from the main post; what's the harm in putting carb heat on for 10 seconds on downwind or base when in the circuit? Could save your life! :ok:

[The Messiah]

POH's are oft written by legals more than engineers.

Remember carby heat provides unfiltered air directly to the engine so that can be a problem if you forget to turn it off after landing at a bumpy dirt strip.

As for saving your life? If you are in the circuit in a 152 shouldn't you be within gliding range of the runway anyway? Furthermore if the conditions favour using carby heat then use it, but don't just stick it on for the sake of it. If you select a system on you should ask, 'why am I selecting this?'

I encourage using the old grey matter whenever possible rather than 'monkey see monkey do'.

[Lodown]

The Messiah, I agree with the use of grey matter even though mine is turning a darker shade of amber every day. However, the grey matter doesn't hold up in court against a POH, and by following the POH, you have a rock solid case against the insurance company. If they have a problem with the procedures, let them take it up with the manufacturer rather than with you and your grey matter.

It's disappointing that it has come to this, but that's the way it works these days. New pilots are not taught to think too hard, but rather just told to follow the checklist. Sigh...

[4SPOOLED]

i was taught as you approach the stall angle (usually with the horn on), carb heat off!!!

I always put carb heat as i turn base, then when i lower full flap turning finals carb heat off....although its been a while since i flown a carby A/C

I also open cowl flaps on final not for cooling, but in case of a GA.....remember the PUFF checks?

[A37575]

4spooled. Recommend you read the manufacture's POH for the aircraft you are flying. You can bet that it doesn't say open the cowl flaps on final just in case you go around. That is absolute rubbish. Who on earth taught you that nonsense.

Just think it through logically. If you have to go - around, you simply follow the POH go-around procedure. If you are going straight into another circuit after the go-around then within less than a minute of going around you will be levelling out and the engine temps will have hardly time to increase and certainly they will be nowhere near limits.

On the other hand if you go-around with the intention to climb through several thousand feet then there is plenty of time to open the cowl flaps if needed. And finally if you haven't read the POH for your aircraft type you should not be flying it in command - or at any other time.

[4SPOOLED]

172rg manual (will check other a/c aswell aswell)

PRE LANDING
1 brakes off
2 undercarriage DOWN & LOCKED
3 Mixture rich
4 Fuel on both & Suff
5 Temps & presses's Green
6 Hatches & Harness secure
7 Cowl Flaps FULL OPEN

They are left open in the event of a GA cause you will more than likely forget to open them. Rember any CSU a/c's engine is only designed for full throttle for a couple of minutes after that you setup the CSU so any additional cooling would be great.

Where did you learn to fly?

Any time i fly a CSU a/c with cowls i always use PUFF turning final

Pitch fine
Under Carriage down locked and confirmed
Flaps full
Cowl Flaps Open

:ok:

[Triple Captain]

It is always interisting reading peoples comments on carby heat. After experiencing carby icing at full throttle in clear air and on the ground (does not apply to gravel rwy), we now teach carby heat on untill you touch down. I find it rather disturbing when pilots I fly with select carby heat off at night with 300 - 400 ft to go. I must admit that even though less occurances have been notied in the northern part of the country, there appears to be somewhat an ignorance to carby icing. Here is a story: http://www.atsb.gov.au/aviation/occurs/occurs_detail.cfm?ID=49

I was always told carby ice occurs at reduced power (more likly in dense air and cold weather).

Considering the original question, what do we loose at full power with carby heat on? Maybe 100 rpm (152 / 172). My suggestion power first.

Another interisting issue is the PUFF checks. 4Spooled mentioned opening cowls on final. An interisting thought: in an aircraft such as a Chieftain, attempting to climb at MTOW on one engine in any kind of day at sea level may not provide the desired RoC. It is interisting to try: Single engine climb in PA31-350 set zero thrust, then reduce power to 0 fpm climb, then close the cowl flaps. It is rather intersting to see how much drag those little flaps cause. You may also notice that at 500' to go in a climb, closing the cowl flaps results in a reasonable airspeed increase.
What is the harm in leaving the cowl flaps closed untill on the ground. If you do have to conduct a go-around - smooth power (or i'll slap your wrists C152 or PA31 alike) the engine is not going to over heat instantly. Just don't forget "Secure the dead" (cowl flap closed) "Look after the live" (cowl flap open).

[Atlas Shrugged]

Rember any CSU a/c's engine is only designed for full throttle for a couple of minutes after that you setup the CSU Where did you hear that?

[Triple Captain]

C206 POH. Engine is only to be operated at full power for less then 3 minutes.