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Author Topic: Bent Pitot Tube  (Read 23704 times)

Brad Beeching

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Bent Pitot Tube
« on: April 21, 2012, 08:05:45 PM »

I was just reading about the takeoff from Lae and was curious about the Bent Pitot Tube.
The pitot tube is used to bring ambient air into the altimeter doesn't it?
Or is it used for the airspeed indicator?
Or both (2 tubes)?
Maybe someone has answered this before, but what could the effect be on the Electra?
If the hole in the tube is presented to the airstream as built, the instrument it is attached to will read as it was calibrated to read correct? Now, if that hole is presented to the airstream at an angle caused by a bent tube, the diameter of the hole in the pitot is in effect reduced is it not? What effect would that have on the flight? Would it have caused the airspeed indicator to read slow? How sensitive are the instruments of that era to damage of that type?

Sorry if this is redundant, I couldn't seem to find any discussion on the matter..

Brad

ps. I reread all of the link I provided and I answered some of my own questions, however since we have nothing better to do 'till July, I'll leave 'em to generate discussion..
Brad

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Malcolm McKay

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Re: Bent Pitot Tube
« Reply #1 on: April 21, 2012, 10:21:30 PM »

I was just reading about the takeoff from Lae and was curious about the Bent Pitot Tube.
The pitot tube is used to bring ambient air into the altimeter doesn't it?
Or is it used for the airspeed indicator?
Or both (2 tubes)?
Maybe someone has answered this before, but what could the effect be on the Electra?
If the hole in the tube is presented to the airstream as built, the instrument it is attached to will read as it was calibrated to read correct? Now, if that hole is presented to the airstream at an angle caused by a bent tube, the diameter of the hole in the pitot is in effect reduced is it not? What effect would that have on the flight? Would it have caused the airspeed indicator to read slow? How sensitive are the instruments of that era to damage of that type?

Sorry if this is redundant, I couldn't seem to find any discussion on the matter..

Brad

ps. I reread all of the link I provided and I answered some of my own questions, however since we have nothing better to do 'till July, I'll leave 'em to generate discussion..

Simply put, as the pitot tube is responsible for providing the means of determining an aircraft's speed, and the speed of the aircraft has to be known so that proper utilisation of the fuel on board can be made then if the pitot is damaged and is providing erroneous information regarding speed such as a lower IAS than the actual then the pilot would be prompted to burn more fuel to bring the aircraft to the desired cruising speed/altitude. Obviously this would effect the actual distance the aircraft could fly by shortening its available range. Equally if the IAS was wrongly given as too high then the aircraft could be throttled back to be dangerously close to stalling speed. All sorts of nasty things can happen if the pitot tube is damaged.
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richie conroy

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Re: Bent Pitot Tube
« Reply #2 on: April 21, 2012, 10:37:11 PM »

reply 932 page 65 some discussion on pitot tubes

https://tighar.org/smf/index.php/topic,571.960.html
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Gary LaPook

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Re: Bent Pitot Tube
« Reply #3 on: April 22, 2012, 01:10:43 AM »

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Jeff Victor Hayden

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Re: Bent Pitot Tube
« Reply #4 on: April 22, 2012, 02:10:59 AM »

Yes a bent pitot tube will give erroneous information regarding airspeed. Even these days airliners fall foul of false information fed to the computers by faults related to the pitot tubes. Garys explanation regarding the fuel consumption errors associated with such a problem are significant in AE's case.

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Brad Beeching

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Re: Bent Pitot Tube
« Reply #5 on: April 22, 2012, 07:44:13 AM »

In reading about the Bent Pitot Tube, it states that the tube(s) provided ram air to the airspeed indicators. And if it were bent, it would make that indicator read slower? Can we know from the angle of the tube how much slower that indicator might have been off?

So if she had one indicator that was reading slower, and the other (being undamaged) we'll assume is correct. If she looked at both indicators and saw one was a bit off, how much does that effect her piloting?

Brad
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Malcolm McKay

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Re: Bent Pitot Tube
« Reply #6 on: April 22, 2012, 07:52:38 AM »

If she looked at both indicators and saw one was a bit off, how much does that effect her piloting?

Brad

Rather depends on how distorted the inside of the tube was, if it was bent, and that is rather impossible to tell at this distance in time.
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Brad Beeching

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Re: Bent Pitot Tube
« Reply #7 on: April 22, 2012, 08:29:43 AM »

I rather expected as much. It was just curiosity. I've been trying to grasp the picture of the disappearance as a whole. It appears there was alot of damage to the airplane that impacted her ability to find Howland. It wasn't just that she didn't understand Morse Code, or was just stubborn or that she just held a course too far one way or another. One bit seems to have compounded another and impacted another and so on and so on, until the airplanes flew away and she knew, I mean really knew that no one would be coming.

Brad
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Andrew M McKenna

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Re: Bent Pitot Tube
« Reply #8 on: April 22, 2012, 08:37:46 AM »

We spent a lot of bandwidth on this once upon a time, and , if memory serves, it was finally determined through forensic imaging analysis of the photo and take off film by none other than Jeff Glickman that that pitot tube was not bent or damaged as it appears.  More of an optical illusion brought on by the angle of the photo or something like that.

See the update at the top of the research bulletin on the Lost Antennahttp://tighar.org/Projects/Earhart/Archives/Research/Bulletins/26_Antenna2/26_Antenna2.html

Update, 11/25/01

Subsequent analysis by Photek has determined that the “bent” pitot tubes are an optical illusion and were, in fact, undamaged at the time of takeoff. The conclusion that the belly antenna is missing remains unchanged.


Andrew
« Last Edit: April 22, 2012, 09:10:50 AM by Andrew M McKenna »
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Martin X. Moleski, SJ

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Re: Bent Pitot Tube
« Reply #9 on: April 22, 2012, 08:49:57 AM »

I rather expected as much. It was just curiosity. I've been trying to grasp the picture of the disappearance as a whole. It appears there was alot of damage to the airplane that impacted her ability to find Howland. It wasn't just that she didn't understand Morse Code, or was just stubborn or that she just held a course too far one way or another. One bit seems to have compounded another and impacted another and so on and so on, until the airplanes flew away and she knew, I mean really knew that no one would be coming.

I think that is what people mean when they talk about an "accident chain."  Hindisight is 20-20 vision.  After 12 years of reading about TIGHAR's work, I feel confident that the major links in this chain have been found.

If one link in the chain had been removed, the chain would have broken.

Small things add up.  "The devil is in the details."

The hard part is recognizing an accident chain before the accident happens.  I drove a car off the road and into a retaining wall in November.  I wish I could have that night back with the benefit of hindsight.   :(

Here's the last link in my accident chain, for inquiring minds and safety-conscious drivers: don't use cruise control on slippery roads.  If anybody ever mentioned that to me, I wasn't listening.  I took driver's ed in 1966, and the proper use of cruise control was not on our curriculum because the device wasn't available in most of the cars on the road back then.   ::)
LTM,

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« Last Edit: April 22, 2012, 08:54:02 AM by Martin X. Moleski, SJ »
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Brad Beeching

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Re: Bent Pitot Tube
« Reply #10 on: April 22, 2012, 09:51:59 AM »

Quote
Update, 11/25/01
Subsequent analysis by Photek has determined that the “bent” pitot tubes are an optical illusion and were, in fact, undamaged at the time of takeoff. The conclusion that the belly antenna is missing remains unchanged.

Mr. McKenna, I didn't see where the bulletin was updated, is that info somewhere else perhaps? Or did I just miss it? In any case, thats one heck of an illusion!  ;D

Quote
for inquiring minds and safety-conscious drivers: don't use cruise control on slippery roads.

Mr. Moleski, Here is something else not taught in driving schools. If you are on ice in an automatic, kick it out of drive when you need to stop. Automatics seem to keep "driving" even when the brakes are applied. Try it next winter in a safe place, you'll be surprised at how fast you can stop.

Brad
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Martin X. Moleski, SJ

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Re: Bent Pitot Tube
« Reply #11 on: April 22, 2012, 10:21:27 AM »

Mr. Moleski, Here is something else not taught in driving schools. If you are on ice in an automatic, kick it out of drive when you need to stop. Automatics seem to keep "driving" even when the brakes are applied. Try it next winter in a safe place, you'll be surprised at how fast you can stop.

BTDT and agree that that is the best technique for an emergency stop.

I've been driving on ice and snow in the Northeast since 1968.  As a general rule, I don't use the breaks when trying to correct a skid.  It wasn't until hours after the accident that I could answer the question why everything I did made the fishtailing worse rather than better.  Answer: the cruise control was driving the wheels at the equivalent of 65 mph while the the car's groundspeed was less than that.  Of course, if I hadn't been distracted by finishing a cup of coffee and trying to figure out the lyrics of a song on the radio, I probably wouldn't have lost control of the car in the first place.  That's the dumb thing about accidents.  They happen when I don't expect them.   :-[
LTM,

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Andrew M McKenna

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Re: Bent Pitot Tube
« Reply #12 on: April 22, 2012, 11:16:43 AM »

The research bulletin is dated August 10, 2000

Look right at the top of the page  http://tighar.org/Projects/Earhart/Archives/Research/Bulletins/26_Antenna2/26_Antenna2.html

and you should see the box that has the update

Update, 11/25/01

Subsequent analysis by Photek has determined that the “bent” pitot tubes are an optical illusion and were, in fact, undamaged at the time of takeoff. The conclusion that the belly antenna is missing remains unchanged.

amck
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Brad Beeching

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Re: Bent Pitot Tube
« Reply #13 on: April 22, 2012, 11:53:20 AM »

 ::) Well.... there you go... if you want to hide something from me.... put it right out in front where everyone else can see it!
Brad

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Jeff Victor Hayden

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Re: Bent Pitot Tube
« Reply #14 on: April 22, 2012, 12:50:04 PM »

Brad, here's a link that shows some of the problems associated with pitot tubes and their consequences. There's a lot of these incidents on aircrash investigation on youtube...

http://voices.yahoo.com/plane-crashes-pitot-tubes-2447529.html
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