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airspeed problems

Sam Intel Guest

I was flying to ANC today a My airnd I just took off in a 757-200.speed and back-up airspeed indicators went to zero about a minute in, but I am not getting a stall alarm, and my GPS says that my ground speed 533 kts. It is very diffucult to fly with having no idea what your airspeed is, and I can't get it to work. Dose any body know what is wrong?

8 Responses

Pro Member Chief Captain
Alex (Fire_Emblem_Master) Chief Captain

Turn ON the switch labeled "PITOT HEAT"

The tube that measures air speed and other stuff is freezing over/something else is happening to it

It takes about 1-2 minutes for it to re thaw.

LEAVE IT ON after you turn it on!

Sam Intel Guest

Thanks, I'll try that.

Don Wood Guest

I agree it is probably a pitot tube freezing. I don't fly anything that big in either real life or in the sim, however, I suggest you review the checklist for the aircraft you are flying. Any aircraft I have ever been exposed to that is approved for flight into known icing conditions has a checklist item to turn on pitot heat when OAT (Outside air Temp) reaches a point slightly above freezing, usually around 4 degrees C.

Guest Ed Guest

It would be nice if more of the sim aircraft gave you an OAT readout-- the Lear Jet does, but I don't think many of the smaller planes do.

Ed

Don Wood Guest

Most planes have some OA temperature indicator even if it's only a thermometer. You can make a thumbnail estimate if you do not have an indicator. Take ground temperature and decrease it by 2 degrees fairenheit for every thousand feet of altitude. It won't be exact but, barring some sort of inversion or other weather anamoly, it will be close.

When I'm flying an aircraft with a heated pitot, I treat it the same way I do carbuerator heat. If I'm in doubt whether its needed or not, I turn it on. Like many other things in flying, its better to use it and not need it than it is to need it and not use it.

Pro Member First Officer
horrgakx First Officer

I've never had that happen, even at 35,000+. How come?
(all realism settings are max)

Pro Member Captain
John Hodges (originalgrunge) Captain

I've never had that happen, even at 35,000+. How come?
(all realism settings are max)

What season do you fly in? If you fly routes like SFO to HNL or something warm like that, you'll probably not find a problem with it freezing. You won't find too much trouble up at FL350, even when the OAT reads -40, since there's very little stuff up there that could freeze your plane. You're mostly going to find it at places with moisture that could ice over.

Pro Member First Officer
PH First Officer

It is generally when you pop in and out of cloud, climb, descent. Due to the friction caused by the airflow over the ac in the cruise with OAT -50 etc the pitot is nowhere near as cold. For those of you that have flown or fly Concorde you can see the skin temp gets very hot at Mach 2! Enough to expand the ac enough to fit your hand in between the panels....just remember to take them out before descent!!

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