jamesbaldwyn
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Pitot Heat, Please Explain

Tue Dec 26, 2006 10:41 pm

Could somebody please quickely explain about Pitot Heat, what it does, when its used and who uses it?

Thanks Guys!
 
IAHFLYR
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RE: Pitot Heat, Please Explain

Tue Dec 26, 2006 11:07 pm

The pitot tube measures the flow of air into the opening at the end of the tube and provides the pilot with airspeed. Pitot heat is turned on by the pilot anytime ice is suspected in order to melt any which might freeze over the tube and create an erroneous reading or no reading at all on the airspeed indicator.
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PhilSquares
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RE: Pitot Heat, Please Explain

Wed Dec 27, 2006 12:52 am

Quoting IAHFLYR (Reply 1):
The pitot tube measures the flow of air into the opening at the end of the tube and provides the pilot with airspeed. Pitot heat is turned on by the pilot anytime ice is suspected in order to melt any which might freeze over the tube and create an erroneous reading or no reading at all on the airspeed indicator.

On the 744, pitot heat is automatically turned on once aircraft power is established.
Fly fast, live slow
 
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Starlionblue
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RE: Pitot Heat, Please Explain

Wed Dec 27, 2006 1:10 am

Quoting IAHFLYR (Reply 1):
The pitot tube measures the flow of air into the opening at the end of the tube and provides the pilot with airspeed. Pitot heat is turned on by the pilot anytime ice is suspected in order to melt any which might freeze over the tube and create an erroneous reading or no reading at all on the airspeed indicator.

Just to give an idea of how important the correct functioning of the pitot system is , check out http://aviation-safety.net/database/record.php?id=19961002-0&lang=en. Masking tape placed on the ports for washing was not removed before flight, and the aircraft crashed at night since the pilots were disoriented and lacking instrumental altitude/speed references.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
jamesbaldwyn
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RE: Pitot Heat, Please Explain

Wed Dec 27, 2006 1:22 am

It looks serious I will pay more attention to the switch now in my simulator. I have just started my PPL training and it was one switch I didnt understand and forgot to ask my insturcter about.

Thanks for your help guys!!
 
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Starlionblue
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RE: Pitot Heat, Please Explain

Wed Dec 27, 2006 1:58 am

Quoting Jamesbaldwyn (Reply 4):
I have just started my PPL training and it was one switch I didnt understand and forgot to ask my insturcter about.

While it's all well and good in visual conditions, if you're stuck in a cloud at night knowing the correct altitude and speed takes on a whole new level of importance.  Wink
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
jamesbaldwyn
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RE: Pitot Heat, Please Explain

Wed Dec 27, 2006 3:55 am

Quoting Starlionblue (Reply 5):

I bet it would, cheers mate
 
EMBQA
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RE: Pitot Heat, Please Explain

Wed Dec 27, 2006 3:57 am

Quoting PhilSquares (Reply 2):
On the 744, pitot heat is automatically turned on once aircraft power is established.

I've never heard of that on any plane. Most will not come on until the plane is in the air. If they come on while on the ground and without an airflow they can be damaged by the heat....and they get very hot.
"It's not the size of the dog in the fight, but the size of the fight in the dog"
 
jamesbuk
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RE: Pitot Heat, Please Explain

Wed Dec 27, 2006 4:15 am

Quoting Jamesbaldwyn (Reply 4):

In my training so far, I've only used it once and that was in very cold conditions (-6 at the altitude we were at) so we plonked it on. Again as people have said its only for cold conditions or if you feel unsure that your instruments are correct. Also i dont think FS simulates it, and its just a button, but id recommend using it in FS so you create awareness of the feature  Smile.

Quoting Starlionblue (Reply 5):

And so do them little engine noises that your sure you've heard before, but are still uneasy  silly 

Rgds --James--
You cant have your cake and eat it... What the hells the point in having it then!!!
 
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Starlionblue
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RE: Pitot Heat, Please Explain

Wed Dec 27, 2006 4:20 am

Quoting Jamesbuk (Reply 8):
Also i dont think FS simulates it, and its just a button,

Nono. It actually sticks a pipe out of your case and measures the geek coefficient present in the room based on exhaled phlogiston. Big grin
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
fr8mech
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RE: Pitot Heat, Please Explain

Wed Dec 27, 2006 5:20 am

Quoting EMBQA (Reply 7):
Most will not come on until the plane is in the air.

I don't know about the B747-400, but pitot heat normally becomes active on the ground with engines running (low heat) and then switches mode in the air (high heat). The system is fully automatic. The crew only learns about failures through EICAS or ECAM and an associated light.
When seconds count...the police are minutes away.
 
KELPkid
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RE: Pitot Heat, Please Explain

Wed Dec 27, 2006 5:56 am

Quoting Jamesbuk (Reply 8):
In my training so far, I've only used it once and that was in very cold conditions (-6 at the altitude we were at) so we plonked it on. Again as people have said its only for cold conditions or if you feel unsure that your instruments are correct. Also i dont think FS simulates it, and its just a button, but id recommend using it in FS so you create awareness of the feature Smile.

At the part 141 school I got my instrument at, there was a checklist for entering clouds(!). It was very simple: Strobes-off (to avoid flash blinding) Pitot Heat-on.

Depending on how the pitot tube ices up (i.e. whether or not the drain hole gets iced as well), you could end up with either a non-functioning airspeed indicator, or an airspeed indicator that acts as an altimeter (a very dangerous situation if not recognized). Because of the locale I trained at for my instrument (Oregon USA, home of the unreported light rime icing buildup  Wink ) we were very consciencious of checking the pitot heat's proper operation on the ground before flight (required for any actual IFR by the flight school).
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OPNLguy
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RE: Pitot Heat, Please Explain

Wed Dec 27, 2006 6:20 am

Quoting Jamesbaldwyn (Thread starter):
Could somebody please quickely explain about Pitot Heat, what it does, when its used and who uses it?

Here's an object lesson in what happens when it's not used...

http://aviation-safety.net/database/record.php?id=19741201-1&lang=en

This accident never got much media attention since only the 3 flightcrew were onboard, and because it occurred on the same day that TWA514 crashed while on approach to IAD, which killed all aboard...

[Edited 2006-12-26 22:51:24]
ALL views, opinions expressed are mine ONLY and are NOT representative of those shared by Southwest Airlines Co.
 
flight152
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RE: Pitot Heat, Please Explain

Wed Dec 27, 2006 7:31 am

Quoting KELPkid (Reply 11):
It was very simple: Strobes-off (to avoid flash blinding) Pitot Heat-on.

Interesting. The 172SP models have their strobes designated as the anti-collision light. They cannot be turned off in clouds.
 
oly720man
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RE: Pitot Heat, Please Explain

Wed Dec 27, 2006 7:40 am

Quoting IAHFLYR (Reply 1):
The pitot tube measures the flow of air into the opening at the end of the tube and provides the pilot with airspeed.

Strictly speaking there isn't any flow into the pitot tube, rather the instrument in the aircraft measures the pressure difference between the total pressure (at the hole in the front of the pitot tube) and the static pressure (on the surface of the fuselage), this difference being the dynamic pressure - with (possibly) some correction due to flow acceleration around the fuselage.
wheat and dairy can screw up your brain
 
KELPkid
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RE: Pitot Heat, Please Explain

Wed Dec 27, 2006 7:54 am

Quoting Flight152 (Reply 13):
Interesting. The 172SP models have their strobes designated as the anti-collision light. They cannot be turned off in clouds.

Every 172P (not SP  Wink ) I've ever flown has a separate strobe and anticollision beacon (either rotating light or electronically pulsated-the big red light on the tail). The strobes are on the wingtips, next to the nav lights.
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N353SK
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RE: Pitot Heat, Please Explain

Wed Dec 27, 2006 8:11 am

Quoting EMBQA (Reply 7):
..and they get very hot.

heh... I've seen them melt marshalling wands before. Why a ramper would think it's OK to rest a wand on a pitot tube is beyond me though...
 
KELPkid
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RE: Pitot Heat, Please Explain

Wed Dec 27, 2006 8:22 am

Quoting N353SK (Reply 16):
Quoting EMBQA (Reply 7):
..and they get very hot.

heh... I've seen them melt marshalling wands before. Why a ramper would think it's OK to rest a wand on a pitot tube is beyond me though...

Try a vinyl or plastic pitot tube cover on a freshly heated pitot tube sometime...  melting 
Celebrating the birth of KELPkidJR on August 5, 2009 :-)
 
flight152
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RE: Pitot Heat, Please Explain

Wed Dec 27, 2006 12:08 pm

Quoting KELPkid (Reply 15):
Every 172P (not SP ) I've ever flown has a separate strobe and anticollision beacon (either rotating light or electronically pulsated-the big red light on the tail). The strobes are on the wingtips, next to the nav lights.

Thats incorrect. The current Skyhawk model in production is the SP and R models. The P ended production in 1985 http://skyhawksp.cessna.com/ The airplane has both a rotation beacon and storbes, however the strobes are certified as the anti-colloision light, unlike all previous 172 models., which means the stobes must be on at all times. If you want to argue, I can photocopy the POH and send it to you.

[Edited 2006-12-27 04:17:41]
 
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HAWK21M
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RE: Pitot Heat, Please Explain

Wed Dec 27, 2006 12:11 pm

Quoting PhilSquares (Reply 2):
On the 744, pitot heat is automatically turned on once aircraft power is established.

Not on the B737 & B757.Any reason.
Those Probes can get Red hot on ground.
regds
MEL
I may not win often, but I damn well never lose!!! ;)
 
boeingfixer
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RE: Pitot Heat, Please Explain

Wed Dec 27, 2006 2:18 pm

Quoting PhilSquares (Reply 2):
On the 744, pitot heat is automatically turned on once aircraft power is established.

The 4 pitot static probes and 2 AOA vanes are only heated when any engine is running on the 744. Due to the nature of the heating elements in the probes, they can't be on for any length of time before flight or the probes will become red hot and probably burn out.

Cheers,

John
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KELPkid
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RE: Pitot Heat, Please Explain

Wed Dec 27, 2006 4:33 pm

Quoting Flight152 (Reply 18):
Thats incorrect.

Okay buddy. I tried to be a gentleman here...

Quoting Flight152 (Reply 18):
The current Skyhawk model in production is the SP and R models.

Glad you have the bucks to rent the most current stuff. It would be better spent elsewhere, however...especially if you are just starting out.

Quoting Flight152 (Reply 18):
The P ended production in 1985 http://skyhawksp.cessna.com/

I could've told you that   Why don't you look up N62348, N63843, N98344, and N54477 in the database and tell me what year and which 172 model those are (the last 4 172's I've logged time in according to my logbook   )

Quoting Flight152 (Reply 18):
The airplane has both a rotation beacon and storbes,

Uh, you mean strobes?  

Quoting Flight152 (Reply 18):
however the strobes are certified as the anti-colloision light, unlike all previous 172 models

Might be true of the SP, I don't know, but I definitely don't remember the instructor saying anything of the sort the one time I flew in an R model (FBO checkout-I decided the extra money for leather and fuel injection wasn't worth it). However, this is definitely not the case in the good ol' P model.

Quoting Flight152 (Reply 18):
If you want to argue, I can photocopy the POH and send it to you.

Not really, and I can acquire the POH from an SP quite easily on my own, thank you very much.

I was just relating my experience, and I gave you the 172 model that I did it in (well, after you tried to flame me...) Kinda wondering why you got all tweaked. Most of the folks in here (tech/ops) aren't looking to jump the other members of the forum at a moment's notice   

[Edited 2006-12-27 08:35:53]
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ThirtyEcho
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RE: Pitot Heat, Please Explain

Wed Dec 27, 2006 4:45 pm

On one of the lessons just prior to my instrument checkride, the airspeed indicator went inop. My instructor turned to me and asked, "You CAN fly an airplane with no airspeed indicator, can't you?" This would be the same as an iced-over pitot tube.

By carefully managing pitch, power and rate of climb/descent indications, it can be done. You have to have memorized desired power settings for desired profiles and configurations but any good IFR pilot has already done that. I already knew that, in a 172 with flaps 10, 700fpm and 1900RPM, I would get an airspeed of 90KIAS down the ILS. It becomes second nature to hit these raw-data numbers before crosschecking the airspeed for confirmation and, then, confirming the overall result with the LOC/GS indications. A good scan will take all of this in, quickly, and apply corrective action, as needed.
 
N231YE
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RE: Pitot Heat, Please Explain

Wed Dec 27, 2006 4:49 pm

Quoting Jamesbaldwyn (Reply 4):
It looks serious I will pay more attention to the switch now in my simulator. I have just started my PPL training and it was one switch I didnt understand and forgot to ask my insturcter about.

My old instructor used to say, If you see visible moisture, then you should use Pitot Heat.
 
ThirtyEcho
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RE: Pitot Heat, Please Explain

Wed Dec 27, 2006 5:14 pm

One more thing about checking your pitot heat in the preflight; be very careful when you touch it to check for operation, the li'l sucker can get very hot.

Remember that pitot heat is an anti-ice system and not a deice system. The intended use is to keep the pitot free of ice and not to remove a thick layer of ice that has already formed.

Watch the OAT. Ice can form without any visible moisture in the vicinity to warn you of its onset, especially if you are under an overcast.

If you want to examine how 172 windshield heat works to defrost an opaque ice coating, go out with your instructor and practice landings by squinting with one eye through a toilet paper tube.
 
jamesbaldwyn
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RE: Pitot Heat, Please Explain

Wed Dec 27, 2006 5:41 pm

Quoting Jamesbuk (Reply 8):
Also i dont think FS simulates it, and its just a button

I'm not sure about FS2004 but FSX certinly does,

Quoting ThirtyEcho (Reply 24):
If you want to examine how 172 windshield heat works to defrost an opaque ice coating, go out with your instructor and practice landings by squinting with one eye through a toilet paper tube.

 lmao  That'll do it. Simple but effective
 
MD11Engineer
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RE: Pitot Heat, Please Explain

Wed Dec 27, 2006 8:07 pm

Quoting EMBQA (Reply 7):
Quoting PhilSquares (Reply 2):
On the 744, pitot heat is automatically turned on once aircraft power is established.

I've never heard of that on any plane. Most will not come on until the plane is in the air. If they come on while on the ground and without an airflow they can be damaged by the heat....and they get very hot.

On the 757 pitot heat comes on automatically when the first engine is running, through the oil pressure switch (this is why you have to remove the pitot covers before doing a ground run).
The 737NG, like it's ancestors is completely manual.

Quoting HAWK21M (Reply 19):
Quoting PhilSquares (Reply 2):
On the 744, pitot heat is automatically turned on once aircraft power is established.

Not on the B737 & B757.Any reason.
Those Probes can get Red hot on ground.
regds
MEL

I know. I learned it years ago when I tried to stick pitot covers on a 727 and discovered the hard way that the pilot had forgotten to turn off pitot heat. Ouch  ouch 

Jan
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Mir
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RE: Pitot Heat, Please Explain

Thu Dec 28, 2006 12:55 am

Quoting Flight152 (Reply 18):
the strobes are certified as the anti-colloision light, unlike all previous 172 models., which means the stobes must be on at all times.

Not true. FAR 91.209 (b) says that while the anti-collision lights should be on at all times, the PIC has the authority to them off if they determine that current operating conditions make it safer to do so. Turning them off in clouds so that they aren't disorienting (particularly at night) is a perfect example of this.

-Mir
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fr8mech
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RE: Pitot Heat, Please Explain

Thu Dec 28, 2006 1:04 am

Quoting MD11Engineer (Reply 26):
through the oil pressure switch

Jan,

You sure it's the oil pressure switch and not the speed card?
When seconds count...the police are minutes away.
 
mrocktor
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RE: Pitot Heat, Please Explain

Thu Dec 28, 2006 1:28 am

Quoting ThirtyEcho (Reply 22):
would be the same as an iced-over pitot tube.

Only if you know it is iced over...
 
MD11Engineer
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RE: Pitot Heat, Please Explain

Thu Dec 28, 2006 4:09 pm

Quoting Fr8Mech (Reply 28):
Quoting MD11Engineer (Reply 26):
through the oil pressure switch

Jan,

You sure it's the oil pressure switch and not the speed card?



Quoting Fr8Mech (Reply 28):
Quoting MD11Engineer (Reply 26):
through the oil pressure switch

Jan,

You sure it's the oil pressure switch and not the speed card?

Just from memory and not looking it up I'd say the signal comes from the oil pressure switch and pitot heat goes on as soon as the oil pressure rises on engine start. Currently I'm only working on 737-800s and I'll need to look it up in my course notes over weekend.

Jan
Je Suis Charlie et je suis Ahmet aussi
 
Tristarsteve
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RE: Pitot Heat, Please Explain

Thu Dec 28, 2006 7:29 pm

Quoting Fr8Mech (Reply 28):
You sure it's the oil pressure switch and not the speed card?

Pitot heat is selected on through the speed cards. First engine running selects pitot heat on. It also goes through air/ground sense so it stays powered in flight with engines not running. AoA probes are the same.
The difference is TAT probe. This is only powered in flight, but the failure light goes out at the same time as the pitot heat, i.e. on engine start, but the probe does not receive power until airbourne.

When I used to fly in the Tristar, I remember the final checks before take off was TAT probe heat on. The flight engineer used to keep his finger on the switch and push it in as the throttles were advanced.
 
Woosie
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RE: Pitot Heat, Please Explain

Fri Dec 29, 2006 12:52 am

Quoting EMBQA (Reply 7):
Quoting PhilSquares (Reply 2):
On the 744, pitot heat is automatically turned on once aircraft power is established.

I've never heard of that on any plane. Most will not come on until the plane is in the air. If they come on while on the ground and without an airflow they can be damaged by the heat....and they get very hot



Quoting Fr8Mech (Reply 10):
Quoting EMBQA (Reply 7):
Most will not come on until the plane is in the air.

I don't know about the B747-400, but pitot heat normally becomes active on the ground with engines running (low heat) and then switches mode in the air (high heat). The system is fully automatic. The crew only learns about failures through EICAS or ECAM and an associated light.

My understanding of pitot heat is that it goes on automatically when in flight and can be switched ON on ground; how much heat output and what conditions it comes on on ground is different from type to type. In other words, when it comes on for a 737NG may be different than a 777. Douglas products use the same basic philosophy amongst twinjets, trijet and the DC-8.

I look to the Wiring Diagrams to tell me how a particular type works.
 
jamesbuk
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RE: Pitot Heat, Please Explain

Fri Dec 29, 2006 2:05 am

Quoting ThirtyEcho (Reply 22):

I've had to do a similar thing in a C152, I knew what power settings were used for when so we flew like that, turnt out to be one of my most succesfull flights!

Rgds --James--
You cant have your cake and eat it... What the hells the point in having it then!!!
 
Illini_152
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RE: Pitot Heat, Please Explain

Fri Dec 29, 2006 4:23 am

Quoting Fr8Mech (Reply 28):
the strobes are certified as the anti-colloision light, unlike all previous 172 models., which means the stobes must be on at all times.

No, it means that either the rotating beacon OR the strobes must be on unless, as already posted 14CFR91.209 that the PIC determines that safety precludes their use. This also means you can extinguish the beacon in IMC as well; makes sense- nobody can see you anyway, and I always found it particularly distracting when freight doggin' it.

Many Wheelen strobe STC's are required to be turned off when operating in IMC, even if they are the only anti-collision light installed. Another time you'd want to exercise that PIC authority is on a crowded ramp at night- nav lights are on, they can see you. No sense in blinding everybody else with your strobes too.

Did that many times when flying 402's with only strobes installed, or combined beacon/strobe switches. Running engines and nav lights are enough in those conditions; safer than blinding everybody else on the ramp.

Cessna certified them this way in the newer Skyhawk models so that you could still dispatch if the rotating beacon went tango-uniform.
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bingo
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RE: Pitot Heat, Please Explain

Fri Dec 29, 2006 12:13 pm

Quote:
Just to give an idea of how important the correct functioning of the pitot system is , check out http://aviation-safety.net/database/record.php?id=19961002-0&lang=en. Masking tape placed on the ports for washing was not removed before flight, and the aircraft crashed at night since the pilots were disoriented and lacking instrumental altitude/speed references.

I remember this incident. http://aviation-safety.net/database/record.php?id=19960206-0&lang=en
they brought a lot of the bodies into San Juan, PR. Similar circumstances with the Pitot Tubes being blocked.
 
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HAWK21M
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RE: Pitot Heat, Please Explain

Fri Dec 29, 2006 12:52 pm

Thats why Streamers & use of correct tape is very Important.
regds
MEL
I may not win often, but I damn well never lose!!! ;)
 
BAE146QT
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RE: Pitot Heat, Please Explain

Thu Jan 04, 2007 9:42 pm

Quote:
I'm not sure about FS2004 but FSX certinly does,

Affirmative, I've been caught out by it on a handful of occasions. Once was flying a 744 UUDD-EGLL in midwinter. Nighttime and snow. Airspeed didn't come active on takeoff roll so I aborted. Took me a few minutes to work out what I had done wrong.

Its realistic in the sense that it works, but obviously not in the sense that it didn't come on automatically on my 744.
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