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Temperature / pitot heat (Read 1095 times)

Sep 11^th, 2009 at 11:17pm

Capt.Propwash Offline
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this is more geared for Flight Sim flying, but I know that you real world pilots would know more of the answer than anyone else.

In setting up for a flight, and I set the temperature for 95 degrees F (hot and humid South Carolina summer), how would I go about figuring out what my Temperature Aloft is going to be, to know if I need Pitot Heat or not? Is there a general altitude that I should turn on Pitot Heat no matter what the temperature is on the ground?

Granted if the Temp on the ground is below 70, I would probably need heat even at 10,000 AGL; but if the temp is 90 - 100 at the surface, do I still need it at 10,000 AGL?

Just trying to get the most realistic settings and experience out of FS9.

The thoughts and expressions contained in the post above are solely my own, and not necessarily those of Simviation.com, its Moderators, its Staff, its Members, or other guests. They can not, are not, and will not be held liable for any thoughts, or expressions, or posts that I have made, or will make in the future.

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Reply #1 - Sep 12^th, 2009 at 3:56am

Splinter562 Offline
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Tampa, FL

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I guess there are two parts to your question. First is figuring out temperature aloft. The quick way to do this is to use the standard lapse rate of 2°C (3.5°F) per 1,000ft. For example, if the airport is at 1,000ft MSL and the temperature is 35°C and you want to find the temperature at 10,000ft, you should subtract 2°C for every 1,000ft of altitude change. That puts the temperature at 10,000ft MSL at about 17°C for those conditions. If you want a little more accurate temperature information you can get it from various aviation weather products such as the winds aloft:
http://aviationweather.gov/products/nws/winds/

The second part of your question is about when to use pitot heat. In reciprocating engine aircraft, pitot heat is typically turned on prior to flight into visible moisture. This is usually done even if the temperature is above freezing. If the temperature is around freezing but there is no visible moisture, there is no need for pitot heat. Most jet aircraft will leave the pitot heat on for the entire duration of the flight, regardless of the weather conditions.

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Reply #2 - Sep 12^th, 2009 at 4:21am

C Offline
Colonel
Earth

Posts: 13144

Splinter562 wrote on Sep 12^th, 2009 at 3:56am:

The second part of your question is about when to use pitot heat. In reciprocating engine aircraft, pitot heat is typically turned on prior to flight into visible moisture. This is usually done even if the temperature is above freezing. If the temperature is around freezing but there is no visible moisture, there is no need for pitot heat. Most jet aircraft will leave the pitot heat on for the entire duration of the flight, regardless of the weather conditions.

Indeed. I don't think there are too many disadvantages to having it on all the time anyway.

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Reply #3 - Sep 12^th, 2009 at 4:41am

Fozzer Offline
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An elderly FS 2004 addict!
Hereford. England. EGBS.

Posts: 24861

C wrote on Sep 12^th, 2009 at 4:21am:

Splinter562 wrote on Sep 12^th, 2009 at 3:56am:

The second part of your question is about when to use pitot heat. In reciprocating engine aircraft, pitot heat is typically turned on prior to flight into visible moisture. This is usually done even if the temperature is above freezing. If the temperature is around freezing but there is no visible moisture, there is no need for pitot heat. Most jet aircraft will leave the pitot heat on for the entire duration of the flight, regardless of the weather conditions.

Indeed. I don't think there are too many disadvantages to having it on all the time anyway.

I think the Pitot Tube does consume a fair few Amps from the Power supply, which probably affects smaller GA Aircraft with limited Battery Power.

..and of course, those of us with piston prop, normally aspirated engines, also have to remember to apply our Carburetor Heat at regular intervals, (especially before closing the Throttle), the prevent Carburettor Icing! ....again this puts a strain on the Battery if left on unnecessarily.

Its always a good idea to remember to apply Pitot Heat, and Carburettor Heat at regular intervals during the flight, whilst keeping a careful watch on the instruments, and listen to the sound of the sound of the Engine(s) for possible malfunction...It will help in the "Real Flight"...

...!

Paul

« Last Edit: Sep 12^th, 2009 at 4:45pm by Fozzer »

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Reply #4 - Sep 12^th, 2009 at 4:51am

Hagar Offline
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Fozzer wrote on Sep 12^th, 2009 at 4:41am:

..and of course, those of us with piston prop, normally aspirated engines, also have to remember to apply our Carburetor Heat at regular intervals, (especially before closing the Throttle), the prevent Carburetor Icing! ....again this puts a strain on the Battery if left on unnecessarily.

I think you're getting confused here Paul. Carburettor heating on a normally aspirated piston engine is done with hot air diverted from the engine exhaust manifold. No electric power is involved. This can reduce the available power from the engine so be careful when you use it.

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Reply #5 - Sep 12^th, 2009 at 5:33am

Fozzer Offline
Colonel
An elderly FS 2004 addict!
Hereford. England. EGBS.

Posts: 24861

Hagar wrote on Sep 12^th, 2009 at 4:51am:

Fozzer wrote on Sep 12^th, 2009 at 4:41am:

..and of course, those of us with piston prop, normally aspirated engines, also have to remember to apply our Carburetor Heat at regular intervals, (especially before closing the Throttle), the prevent Carburetor Icing! ....again this puts a strain on the Battery if left on unnecessarily.

I think you're getting confused here Paul. Carburettor heating on a normally aspirated piston engine is done with hot air diverted from the engine exhaust manifold. No electric power is involved. This can reduce the available power from the engine so be careful when you use it.

...quite right, Doug.... Wink

Wink

...Knickers in a twist again... Embarrassed

Embarrassed

..!

Carb Heat affects the Power available.

I've got so used to applying Carb Heat on all my little Cessna 150/152's, that its now become automatic to use it when necessary....

Apply heat before closing the Throttle prior to landing, and cancel Carb Heat before touch down if an aborted landing becomes necessary and maximum power is required for go-around, ....or a touch-and-go..

...!

..the same Icing problem affected all my "Old" Motor Bikes, and Vintage Motor Car, fitted with Carburettors, in adverse Cold + High Humidity Weather conditions.... Shocked

Shocked

....!

Paul...just heating up a nice Cup of Tetley Tea...

...!

« Last Edit: Sep 12^th, 2009 at 4:53pm by Fozzer »

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Reply #6 - Sep 12^th, 2009 at 10:18am

Brett_Henderson Offline
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When I fly a carburettor equiped airplane, I touch the carb-heat lever any time I touch the throttle, and then decide whether or not to apply it. In most C172s, this is easy, becuase the throttle and carb-heat are next to each other. If you have a large hand, you can grab them simultaneously.

As for pitot heat... I have two, hard rules.

1) Always on while IFR
2) Never on until airborne

A pitot heating element can overheat and burn out while on the ground.

The other good rule to "live" by.. is that if you think pitot ice is possible...you should either be flying IFR, or not flying at all Cool

Cool

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Reply #7 - Sep 12^th, 2009 at 11:12am

-Crossfire- Offline
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Fozzer wrote on Sep 12^th, 2009 at 5:33am:

Hagar wrote on Sep 12^th, 2009 at 4:51am:

Fozzer wrote on Sep 12^th, 2009 at 4:41am:

I think you're getting confused here Paul. Carburettor heating on a normally aspirated piston engine is done with hot air diverted from the engine exhaust manifold. No electric power is involved. This can reduce the available power from the engine so be careful when you use it.

Apply heat before closing the Throttle prior to landing, and cancel Carb Heat before touch down, if an aborted landing becomes necessary and maximum power is required for go-around, ....or a touch-and-go..

...!

I wouldn't be doing anything else right before touchdown except flying the airplane! The flare and landing should have your full attention. You shouldn't be fumbling around with the carb heat. It can be closed after touchdown. Should a go-around be needed, carb heat in, full power!

Also Brett.... #2 - Never on until airborne.

Pitot Heat is usually a line-up checklist item. I always turn it on while taxiing on to the active, along with transponder and lights. If you have to wait awhile before takeoff, then leave it off.

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Reply #8 - Sep 12^th, 2009 at 11:56am

Brett_Henderson Offline
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BE AN NDB

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Since we're splitting hairs

Quote:

I wouldn't be doing anything else right before touchdown except flying the airplane! The flare and landing should have your full attention. You shouldn't be fumbling around with the carb heat. It can be closed after touchdown. Should a go-around be needed, carb heat in, full power!

I turn it off on short final. A go-around could very well be a last second decision where the difference twixt hitting the runway in the manner you're trying to avoid, and climbing away safely will require instant throttle response.. even a worse time to be groping for the carb-heat knob.

Quote:

Also Brett.... #2 - Never on until airborne.

Pitot Heat is usually a line-up checklist item. I always turn it on while taxiing on to the active, along with transponder and lights. If you have to wait awhile before takeoff, then leave it off.

Can't argue with that technique.. I'll admit that it's a personal rule. Turn on course, turn on pitot heat (if IFR).

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Reply #9 - Sep 12^th, 2009 at 1:15pm

Fozzer Offline
Colonel
An elderly FS 2004 addict!
Hereford. England. EGBS.

Posts: 24861

Brett_Henderson wrote on Sep 12^th, 2009 at 11:56am:

Since we're splitting hairs

Quote:

I wouldn't be doing anything else right before touchdown except flying the airplane! The flare and landing should have your full attention. You shouldn't be fumbling around with the carb heat. It can be closed after touchdown. Should a go-around be needed, carb heat in, full power!

I turn it off on short final. A go-around could very well be a last second decision where the difference twixt hitting the runway in the manner you're trying to avoid, and climbing away safely will require instant throttle response.. even a worse time to be groping for the carb-heat knob.

Quote:

Also Brett.... #2 - Never on until airborne.

Pitot Heat is usually a line-up checklist item. I always turn it on while taxiing on to the active, along with transponder and lights. If you have to wait awhile before takeoff, then leave it off.

Can't argue with that technique.. I'll admit that it's a personal rule. Turn on course, turn on pitot heat (if IFR).

That Carb' Heat technique has become second nature for me now, in my little Cessna's....so that I don't forget!.... Wink

Wink

...!

Paul...FS 2004... Cool

Cool

...!

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Reply #10 - Sep 12^th, 2009 at 2:02pm

DaveSims Offline
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Clear Lake, Iowa

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Brett_Henderson wrote on Sep 12^th, 2009 at 11:56am:

Since we're splitting hairs

Quote:

I wouldn't be doing anything else right before touchdown except flying the airplane! The flare and landing should have your full attention. You shouldn't be fumbling around with the carb heat. It can be closed after touchdown. Should a go-around be needed, carb heat in, full power!

I turn it off on short final. A go-around could very well be a last second decision where the difference twixt hitting the runway in the manner you're trying to avoid, and climbing away safely will require instant throttle response.. even a worse time to be groping for the carb-heat knob.

Quote:

Also Brett.... #2 - Never on until airborne.

Pitot Heat is usually a line-up checklist item. I always turn it on while taxiing on to the active, along with transponder and lights. If you have to wait awhile before takeoff, then leave it off.

Can't argue with that technique.. I'll admit that it's a personal rule. Turn on course, turn on pitot heat (if IFR).

In most Cessna's you can push the carb heat in at the same time as applying the throttle, by using your palm to push the throttle and your thumb on the carb heat as you push in. I have also been taught in Pipers to just check the carb heat before landing, but it can be left off. The theory is that on Piper's the carb is surrounded by the oil pan and stays warm enough to avoid ice. Or so I'm told.

Dave

www.flymcw.com

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Reply #11 - Sep 12^th, 2009 at 3:39pm

Capt.Propwash Offline
Colonel
Let's get a little mud
on the tires!
KCHS, Charleston, SC, USA

Gender:
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carb heat. = on BEFORE Idle, off BEFORE bat out of hell. -- gotcha.

pitot heat = (ugh i hate metric scale being i live in Farenheight land) -- (reported ground temp) - 3.5º F / +1000' MSL) = Temp aloft ???

90º summer day at KCHS .. will be flying at FL200 to KMIA VFR.... KCHS @ +46 ft MSL,

so..... may as well get use to turning it on anyways? even though ground temp is 90º.

just flip the switch when atc says "you are cleared for take off"

The thoughts and expressions contained in the post above are solely my own, and not necessarily those of Simviation.com, its Moderators, its Staff, its Members, or other guests. They can not, are not, and will not be held liable for any thoughts, or expressions, or posts that I have made, or will make in the future.

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Reply #12 - Sep 12^th, 2009 at 3:45pm

Fozzer Offline
Colonel
An elderly FS 2004 addict!
Hereford. England. EGBS.

Posts: 24861

The nice thing about the little Cessna Trainers, is the "Aircraft Owners Handbook".

A careful study of that covers most everything, and puts you in good stead for managing most Aircraft... Wink

Wink

...!

Paul....G-BPLF...FS 2004... Cool

Cool

...!

P.S....I wonder how many Simmers actually read it?... Shocked

Shocked

...

Wink

...!

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Reply #13 - Sep 12^th, 2009 at 4:08pm

Hagar Offline
Colonel
My Spitfire Girl
Costa Geriatrica

Posts: 33159

I should point out that quite a lot of light aircraft have no carb heat control or heated pitot head. I'm thinking specifically of the Tiger Moth but there are many others.

Quote:

A careful study of that covers most everything, and puts you in good stead for managing most Aircraft... Wink

Wink

...!

Paul. I've noticed a worrying trend towards Americanisms in your recent posts. First carburetor & now this. Shocked

Shocked

Tongue

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Reply #14 - Sep 12^th, 2009 at 4:41pm

Fozzer Offline
Colonel
An elderly FS 2004 addict!
Hereford. England. EGBS.

Posts: 24861

Hagar wrote on Sep 12^th, 2009 at 4:08pm:

I should point out that quite a lot of light aircraft have no carb heat control or heated pitot head. I'm thinking specifically of the Tiger Moth but there are many others.

Quote:

A careful study of that covers most everything, and puts you in good stead for managing most Aircraft... Wink

Wink

...!

Paul. I've noticed a worrying trend towards Americanisms in your recent posts. First carburetor & now this. Shocked

Shocked

Tongue

Well, Doug...

I was "almost exactly" right... Wink

Wink

...

Tongue

...

Grin

...!

Paul... Grin

Grin

...

Grin

...!

P.S. ..I must ignore the fact that my Firefox Dictionary keeps telling me that there are NOT two "T"'s in Carburettor... Cry

Cry

...!

.... Grin

Grin

....!

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