Sponsor Message:
Aviation Technical / Operations Forum
My Starred Topics | Profile | New Topic | Forum Index | Help | Search 
Freezing Pitot Tubes  
User currently offlineHNLsurfer From United States of America, joined Feb 2009, 47 posts, RR: 0
Posted (2 years 10 months 1 day 7 hours ago) and read 6387 times:

Why don't they manufacture them with a tiny coil heater to prevent freezing? Or do I not know what I am talking about?

24 replies: All unread, jump to last
 
User currently offlinelonghauler From Canada, joined Mar 2004, 4924 posts, RR: 43
Reply 1, posted (2 years 10 months 1 day 7 hours ago) and read 6386 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
User currently offlinelonghauler From Canada, joined Mar 2004, 4924 posts, RR: 43
Reply 2, posted (2 years 10 months 1 day 7 hours ago) and read 6374 times:

Quoting longhauler (Reply 1):
And yes, pilot tubes are heated.

Good heavens, that almost sounds naughty!
Of course, I meant pitot tubes.  



Never gonna grow up, never gonna slow down .... Barefoot Blue Jean Night
User currently offlineHNLsurfer From United States of America, joined Feb 2009, 47 posts, RR: 0
Reply 3, posted (2 years 10 months 1 day 7 hours ago) and read 6374 times:

Quoting longhauler (Reply 1):

Then are the heaters failing? Or are they not hot enough?


User currently offlineNWAROOSTER From United States of America, joined Feb 2005, 1081 posts, RR: 3
Reply 4, posted (2 years 10 months 1 day 7 hours ago) and read 6310 times:
Support Airliners.net - become a First Class Member!

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.   


User currently offlineCX Flyboy From Hong Kong, joined Dec 1999, 6597 posts, RR: 55
Reply 5, posted (2 years 10 months 1 day 7 hours ago) and read 6233 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.

User currently offlinetype-rated From United States of America, joined Sep 1999, 4974 posts, RR: 19
Reply 6, posted (2 years 10 months 1 day 3 hours ago) and read 5944 times:

Even small aircraft have pitot heat. I have seen it even on a Cessna 150 before.


Fly North Central Airlines..The route of the Northliners!
User currently offlineAA737-823 From United States of America, joined Mar 2000, 5766 posts, RR: 11
Reply 7, posted (2 years 10 months 1 day 3 hours ago) and read 5909 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.


User currently offlineflyhossd From United States of America, joined Nov 2009, 865 posts, RR: 2
Reply 8, posted (2 years 10 months 1 day 1 hour ago) and read 5790 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.
User currently offlineStarlionblue From Greenland, joined Feb 2004, 17015 posts, RR: 67
Reply 9, posted (2 years 10 months 1 day ago) and read 5753 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.

 duck 

[Edited 2011-10-25 01:47:01]


"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlineHAWK21M From India, joined Jan 2001, 31667 posts, RR: 56
Reply 10, posted (2 years 10 months 23 hours ago) and read 5735 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]



Think of the brighter side!
User currently offlineflipdewaf From United Kingdom, joined Jul 2006, 1568 posts, RR: 1
Reply 11, posted (2 years 10 months 23 hours ago) and read 5735 times:
Support Airliners.net - become a First Class Member!

Quoting Starlionblue (Reply 9):
So it is possible to fly with no airspeed indication.

Only if you have back driven throttles!

  

Fred


User currently offlineFabo From Slovakia, joined Aug 2005, 1219 posts, RR: 1
Reply 12, posted (2 years 10 months 22 hours ago) and read 5713 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.



The light at the end of tunnel turn out to be a lighted sing saying NO EXIT
User currently offlineSAAFNAV From South Africa, joined Mar 2010, 271 posts, RR: 1
Reply 13, posted (2 years 10 months 17 hours ago) and read 5633 times:

Quoting Starlionblue (Reply 9):

And you are still among us. So it is possible to fly with no airspeed indication.

Familiar Power with Familiar Attitude will save your behind.
Recognizing that you have to do that in midst of a crisis, that might be something else.

I also do gliding, and we do Blank Panel training. It's quite easy, as you have no engine to drown out the wind noise..

Erich



On-board Direction Consultant
User currently offlineRaginMav From United States of America, joined May 2004, 376 posts, RR: 1
Reply 14, posted (2 years 10 months 16 hours ago) and read 5596 times:

Quoting HNLsurfer (Reply 3):
Then are the heaters failing?
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.


User currently offlineflyhossd From United States of America, joined Nov 2009, 865 posts, RR: 2
Reply 15, posted (2 years 10 months 12 hours ago) and read 5513 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.
User currently offlinecmf From , joined Dec 1969, posts, RR:
Reply 16, posted (2 years 10 months 11 hours ago) and read 5500 times:

Quoting flyhossd (Reply 15):
After landing, I found the circuit breaker to be popped and then reset it.

One circuit for all pitots?


User currently offlineKELPkid From United States of America, joined Nov 2005, 6370 posts, RR: 3
Reply 17, posted (2 years 10 months 9 hours ago) and read 5443 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 :-)
User currently offlineflyhossd From United States of America, joined Nov 2009, 865 posts, RR: 2
Reply 18, posted (2 years 10 months 9 hours ago) and read 5441 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.
User currently offlineN49WA From , joined Dec 1969, posts, RR:
Reply 19, posted (2 years 9 months 1 week 5 days 7 hours ago) and read 4831 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.

User currently offlineHAWK21M From India, joined Jan 2001, 31667 posts, RR: 56
Reply 20, posted (2 years 9 months 1 week 4 days 20 hours ago) and read 4717 times:

Quoting N49WA (Reply 19):
Lesson learned.

Its a Caution in our Basic training.....Even checking is done by tapping lightly to sense heat before covers can be put on.



Think of the brighter side!
User currently offlinerfields5421 From United States of America, joined Jul 2007, 7607 posts, RR: 32
Reply 21, posted (2 years 9 months 1 week 3 days 18 hours ago) and read 4470 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.


User currently offlineThirtyEcho From United States of America, joined Dec 2001, 1645 posts, RR: 1
Reply 22, posted (2 years 9 months 1 week 2 days 6 hours ago) and read 4284 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.

User currently offlineADent From United States of America, joined Dec 2006, 1368 posts, RR: 2
Reply 23, posted (2 years 9 months 1 week 1 day 13 hours ago) and read 4186 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.

User currently offlineKELPkid From United States of America, joined Nov 2005, 6370 posts, RR: 3
Reply 24, posted (2 years 9 months 1 week 1 day 11 hours ago) and read 4160 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 :-)
Top Of Page
Forum Index

Reply To This Topic Freezing Pitot Tubes
Username:
No username? Sign up now!
Password: 


Forgot Password? Be reminded.
Remember me on this computer (uses cookies)
  • Tech/Ops related posts only!
  • Not Tech/Ops related? Use the other forums
  • No adverts of any kind. This includes web pages.
  • No hostile language or criticizing of others.
  • Do not post copyright protected material.
  • Use relevant and describing topics.
  • Check if your post already been discussed.
  • Check your spelling!
  • DETAILED RULES
Add Images Add SmiliesPosting Help

Please check your spelling (press "Check Spelling" above)


Similar topics:More similar topics...
Pitot Tubes Thales posted Tue Jan 5 2010 00:54:01 by Kimon
Pitot Tubes - A330 posted Fri Jun 12 2009 06:32:09 by Mattcian
Blocked Pitot Lines posted Wed Mar 21 2012 02:23:27 by HAWK21M
Looks Like A Pitot Tube? posted Wed Aug 11 2010 02:24:57 by jackmidd
Freezing Rain: What's Protecting The Engine Face? posted Wed Dec 30 2009 09:53:57 by Faro
R.A.T As Pitot Tube Back-up? posted Sat Jul 4 2009 18:18:23 by Simps747
GPS As Pitot Tube Backup? posted Sun Jun 7 2009 14:35:53 by Jawed
Aircraft Tires - Tubes Vs. Tubeless posted Fri Apr 17 2009 15:51:38 by Viscount724
Pitot-Static Systems / Compressibility-Effects posted Sun Sep 14 2008 20:15:56 by Blackbird
Pitot Static Tube Question posted Wed Jun 25 2008 22:04:40 by Blackbird

Sponsor Message:
Printer friendly format