longhauler From Canada, joined Mar 2004, 4316 posts, RR: 36 Reply 1, posted (1 year 7 months 4 weeks 22 hours ago) and read 4364 times:
Quoting HNLsurfer (Thread starter): Why don't they manufacture them with a tiny coil heater to prevent freezing? Or do I not know what I am talking about?
If you don't know the answer, then the question is worth asking.
And yes, pilot tubes are heated.
Never gonna grow up, never gonna slow down .... Barefoot Blue Jean Night
NWAROOSTER From United States of America, joined Feb 2005, 864 posts, RR: 3 Reply 4, posted (1 year 7 months 4 weeks 22 hours ago) and read 4288 times:
Quoting HNLsurfer (Reply 3): Then are the heaters failing? Or are they not hot enough?
The heaters do fail, which can cause them to freeze up. The Pitot Heat is supposed to be checked on the ground on a regular basis. It is also possible for the heaters to loose power due to a faulty circuit breaker or not being turned on.
A light should be illuminated on the overhead panel if the Pitot Heat is not on.
CX Flyboy From Hong Kong, joined Dec 1999, 6364 posts, RR: 56 Reply 5, posted (1 year 7 months 4 weeks 21 hours ago) and read 4211 times:
It should also be noted that in the most severe of thunderclouds, it is possible that ice accretion is faster than the ability of the heated tubes to melt the ice. This can cause problems obviously although normally aircraft that have experienced blockages due to ice have had the blockages clear within a couple of minutes as by then the aircraft is normally out of the cloud causing the problems so the ice has stopped accumulating and the heat does its job to melt the remaining ice. This was also the cause in AF447 where the blockage itself did not last long and once cleared the aircraft became totally serviceable once again.
type-rated From United States of America, joined Sep 1999, 4398 posts, RR: 20 Reply 6, posted (1 year 7 months 4 weeks 18 hours ago) and read 3922 times:
Even small aircraft have pitot heat. I have seen it even on a Cessna 150 before.
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AA737-823 From United States of America, joined Mar 2000, 5386 posts, RR: 11 Reply 7, posted (1 year 7 months 4 weeks 17 hours ago) and read 3887 times:
Quoting HNLsurfer (Reply 3): Then are the heaters failing? Or are they not hot enough?
Well, for the most part, they aren't. Pitot tubes haven't appreciably changed design in many decades.
There's only one model of airliner that seems to have trouble, and even then, it seems to be predominant with one pitot probe manufacturer, rather than the other. Which is why the Directive stated that the probes should be changed to the other brand, as I recall.
Unfortunately for AF447, incorrect pilot response also played a starring role in the tragedy. But, in my humble opinion, the guys didn't really stand a chance- they were given insufficient information from which to make good decisions.
So, to your original question, there isn't typically a problem with pitot probe heat.
flyhossd From United States of America, joined Nov 2009, 552 posts, RR: 1 Reply 8, posted (1 year 7 months 4 weeks 16 hours ago) and read 3768 times:
Pitot heat can also be too strong and trip the circuit breaker. Years ago, one of the aircraft I often flew did just that and within a few minutes, the pitot tube would ice up, leaving me without any airspeed indication to fly by. Despite numerous "write-ups" the operator never fixed it and I came to be quite good at flying with no indicated airspeed.
My statements do not represent my former employer or my current employer and are my opinions only.
Starlionblue From Hong Kong, joined Feb 2004, 15904 posts, RR: 66 Reply 9, posted (1 year 7 months 4 weeks 15 hours ago) and read 3731 times:
Quoting flyhossd (Reply 8): Pitot heat can also be too strong and trip the circuit breaker. Years ago, one of the aircraft I often flew did just that and within a few minutes, the pitot tube would ice up, leaving me without any airspeed indication to fly by. Despite numerous "write-ups" the operator never fixed it and I came to be quite good at flying with no indicated airspeed.
And you are still among us. So it is possible to fly with no airspeed indication.
[Edited 2011-10-25 01:47:01]
"There are no stupid questions, but there are a lot of inquisitive idiots." - from Citadel by John Ringo
HAWK21M From India, joined Jan 2001, 31228 posts, RR: 58 Reply 10, posted (1 year 7 months 4 weeks 14 hours ago) and read 3713 times:
The Heater element in the coil keeps the area around the probe from not freezing.
Common mistake in Maintenance......remove the Pitot covers before running the engines or putting the aircraft in to air mode during Maintenance [On most types]
Fabo From Slovakia, joined Aug 2005, 1111 posts, RR: 1 Reply 12, posted (1 year 7 months 4 weeks 12 hours ago) and read 3691 times:
Quoting flipdewaf (Reply 11): Only if you have back driven throttles!
Or no throttles We were taught to fly without airspeed indicators in gliders, although I suspect icing was not the predominant factor in airspeed indication failure in Blaniks. Mechanical blockage sounds more likely to me in that.
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Quoting AA737-823 (Reply 7): So, to your original question, there isn't typically a problem with pitot probe heat.
Furthermore, airliners have three independent heated pitot tubes. Should one fail, the other two should continue to operate normally.
By extention, the most likely way to have no valid airspeed indication is to have all pitot sources freeze up, as can happen in severe icing conditions.
flyhossd From United States of America, joined Nov 2009, 552 posts, RR: 1 Reply 15, posted (1 year 7 months 4 weeks 2 hours ago) and read 3491 times:
Quoting Starlionblue (Reply 9): And you are still among us. So it is possible to fly with no airspeed indication.
The first time it happened, I was in a descent in icing conditions near CLE. At first, I saw a decrease in airspeed and so I lowered the nose to increase speed. However, the speed continued to decrease and then I thought to check the VSI (I had also noticed that the wind noise was louder than normal). Seeing the the vertical speed was great - and that the airspeed was still decreasing - I now knew the airspeed indication was incorrect.
After landing, I found the circuit breaker to be popped and then reset it.
On the return flight, I heard the circuit breaker pop and flew again without a reliable airspeed indication. Unfortunately, our mechanics were never able to repeat the failure on the ground and so the aircraft was released time and time again.
So yes, pitch and power became (unfortunately) common for me. And yes, I wonder what the crew of AF447 saw and what they believed to be happening (I have no Airbus experience to draw from).
My statements do not represent my former employer or my current employer and are my opinions only.
KELPkid From United States of America, joined Nov 2005, 5962 posts, RR: 4 Reply 17, posted (1 year 7 months 4 weeks ago) and read 3421 times:
Quoting Starlionblue (Reply 9): And you are still among us. So it is possible to fly with no airspeed indication.
Definitely not the most ideal of situations, especially when flying in IMC or night (with no visible horizon). You can be trained to do anything. When I was getting my instrument rating, one would think that the vacuum system was most unreliable, and I would have to fly entire flights partial panel (in most GA planes, the attitude indicator and the DG are vacuum-powered). You can thank your flight instructor with the little rubber instrument covers for that Throw in a hold at an NDB while partial panel (in a plane with nothing but a simple ADF indicator), and cockpit workload goes sky high. To top it off, you are being trained to do it alone at the Private Pilot level, no crew members to sluff the work off onto
I vaguely remember my instructor covering the airspeed indicator a time or two, he usually gave it back to me when I went through the checklists and turned on the pitot heat One time he had me land without it (at the end of a simulated ILS to minimums...). As long as you have a working attitude indicator, everything seems to be okay. In most GA planes, the stall warning system is independent of the pitot system, so you'd at least have warning if you were getting too slow (as long as the stall horn or stall warning tab doesn't get iced! ). You can also use rate of descent/climb and general knowledge of power settings during the various phases of flight to your advantage to keep the airspeed under control... I would take 10 airspeed failures to one actual instance of a vacuum system failure any day and twice on Sundays.
Celebrating the birth of KELPkidJR on August 5, 2009 :-)
flyhossd From United States of America, joined Nov 2009, 552 posts, RR: 1 Reply 18, posted (1 year 7 months 3 weeks 6 days 23 hours ago) and read 3419 times:
Quoting cmf (Reply 16): One circuit for all pitots?
In this case, yes. IIRC, all transports are required to have separate systems to maintain the redundancy of the systems. My story was about a Piper Seneca that I flew (freight) in my first flying job - about 30 years ago (feels like 80). That airplane had only one pitot system.
My statements do not represent my former employer or my current employer and are my opinions only.
N49WA From , joined Dec 1969, posts, RR: Reply 19, posted (1 year 7 months 1 week 2 days 22 hours ago) and read 2809 times:
Not too long ago I was at KHHR to greet our Lear when it landed after a job. Right after engine shutdown I put my hand on the pitot tube (no particular reason, just not thinking about it). The burn blisters took a couple of weeks to heal. Lesson learned.
rfields5421 From United States of America, joined Jul 2007, 6192 posts, RR: 25 Reply 21, posted (1 year 7 months 1 week 1 day 9 hours ago) and read 2448 times:
Quoting AA737-823 (Reply 7): There's only one model of airliner that seems to have trouble, and even then, it seems to be predominant with one pitot probe manufacturer, rather than the other.
Really - I never thought the Boeing 777 was a problem model.
The Thales probe involved in the AF447 crash was deemed to have a very slightly higher than normal failure rate. Those failures occured with greater frequency on the A320 family of aircraft than on the long range aircraft. It was due to the type of flying the aircraft do - the higher number of climbs and descents through known icing that the long range aircraft.
That is why the priority on replacing that model probe on the A320 and B737 sized aircraft than the long range aircraft like the A330/ A340 aircraft, though at Air France - that replacement process had begun when AF447 disappeared.
Yes, Airbus tends to use Thales probes more than Goodrich probes. Thales is part of the general European aircraft industry which supports Airbus. But Thales is a huge company - they even have at least three facilities here in Dallas (They have the old Raytheon plants/ business).
And yet - B777 aircraft with the 'good' Goodrich probes have been documented to fail/ freeze in flight on occasion.
ThirtyEcho From United States of America, joined Dec 2001, 1635 posts, RR: 1 Reply 22, posted (1 year 7 months 6 days 21 hours ago) and read 2262 times:
As mu first instrument instructor asked, after I suffered an airspeed indicator failure under the hood, "You can't fly an airplane without an airspeed indicator?" Silly me, duh, of course I could.
ADent From United States of America, joined Dec 2006, 1188 posts, RR: 1 Reply 23, posted (1 year 7 months 6 days 4 hours ago) and read 2164 times:
The AF447 pitot tubes were only iced over for a short time - under 1 minute. The incorrect speed was displayed for 29 seconds on the left PFD and 54 sec on the ISIS.
KELPkid From United States of America, joined Nov 2005, 5962 posts, RR: 4 Reply 24, posted (1 year 7 months 6 days 2 hours ago) and read 2138 times:
Quoting ADent (Reply 23): The AF447 pitot tubes were only iced over for a short time - under 1 minute. The incorrect speed was displayed for 29 seconds on the left PFD and 54 sec on the ISIS.
Still, the worst time for an airspeed indicator to fail is at cruise, at night, in IMC (or even over the ocean with no visual reference whatsoever!). If you react before trying to diagnose, you might find yourself dead As I recall, the aircraft was in a climb when the first stall warning occurred...
On climbout or approach, you might actually be expecting an airspeed indicator, especially if you know you are descending through or climbing through icing. Blundering through the outer bands of a tropical thunderstorm during cruise with large supercooled droplets (enough to ice up the already heated pitot tubes) is probably the exception rather than the norm.
Celebrating the birth of KELPkidJR on August 5, 2009 :-)
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Throw in a hold at an NDB while partial panel (in a plane with nothing but a simple ADF indicator), and cockpit workload goes sky high. To top it off, you are being trained to do it alone at the Private Pilot level, no crew members to sluff the work off onto 
). You can also use rate of descent/climb and general knowledge of power settings during the various phases of flight to your advantage to keep the airspeed under control... I would take 10 airspeed failures to one actual instance of a vacuum system failure any day and twice on Sundays.
As I recall, the aircraft was in a climb when the first stall warning occurred...
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