EuroHarmony Community Forums
Archive => Other Topics => Old Forum => Real-world aviation => Topic started by: EHM-1199 Philip on November 11, 2006, 07:12:43 pm
-
At what outside temperature, or possibly altitude is pitot heat essential. Is it switched on as a matter of course? What about the de-icing on the jet engines? Is there an accepted outside temperature for this?
-
Outside air temperature is critical from 0 to 20 below ... --Turn on pitot heat during preflight to confirm operation and melt any internal ice - hope this helps ;D
-
Pitot Heat is only whilst the aircraft is in the air. On the ground, it will burn the pitot probe out. It is used when there is moisture in the air and there is a risk of ice forming in the pitot tube. Normally it always used whilst transiting through cloud cover. If it is not activated and ice forms in the tube, the pilot will receive incorrect information about the aircraft speed. There are normally 3 Pitot tubes fitted to large aircraft. One for Captains instruments, one for FO instruments and a backup.
De-icing is normally performed on commercial jets by using heated bleed air to melt ice on leading edges of the airframe and around the air intake and N1 fan blade section of the engines. Normally on most jets the nacelette or metalic ring around the front of the air intake is heated to stop ice forming on the engine as cold moist air passes through the N1 stage compressor. Normally engine and wing de-icing is performed when ice is visible on the air frame or windshield. These days most commercial jets have sensors that detect when ice is present. Engine and airframe de-icing can be performed on the ground, but aircraft will still need to be manually de-iced (usually with an alcohol spray) prior to departure when wings and fueselage are covered in ice or snow.
*EDIT* Sorry, forgot, when on the ground, De-icing is only possible with engines running normally! (Unless the aircraft uses a spray system such as the one on the Cessna Citation) Usually after the main engine packs are selected and switched over from the APU pack Wing and Engine De-Icing is selected in low temprature, moist air conditions. (I may be wrong on this as I am going from memory of my checklists but I am sure it is selected before taxi)
-
..........:o - about ten times better then my guess of an explanation ha ha nice to learn new things thanks Phil ;D
-
Very nice explanation, but I haven't understood one thing yet, can you continue using the Pitot heat all flight long, or can it cause damage? I usually turn on pitot just after switching on the engines, and the de-icing when the atmo temperature is around 10-5C...is it ok, or wrong??
Thx in advance
-
As far as I am aware although I am not a RW pilot so coul be wrong,
Pitot Heat can be used in flight, all flight. Only in still air should it not be activated, when air is not passing in to the Pitot tube.
De-Icing can be used at any time but does have a detrimental effect on Fuel Efficiency.
-
Ah, ok...thx for the help Phil ;)
-
In the 737, switching on Pitot Heat (called probe heat in Boeing lingo) is done right after engine start. It can be used whenever the plane has some air coming at it so as not to melt the tube.
Icing equipment is only when used when needed - i.e the temperature is between +3 and -20 (any more there's no risk of icing, less and the ice is too cold to stick to the plane) and there is moisture in the air.
-
Wow! Fascinating and detailed replies, thanks guys. Never would have realised that below -20 there is no ice formation. My use of pitot heat and de-icing will be better informed now. Thanks again.
-
Well if it improves your simulator experience, then that is great! My dad was an Electronics Engineer in the RAF and one of his responsibilities was replacing Probes on VC10's after Pilots had left them on and burnt them out!
-
I just found a really interesting web link about the problems of icing in flight- well worth a look!
http://aircrafticing.grc.nasa.gov/courses.html
If you've got a few spare minutes take a look!