The Watering Hole: September 24 – Pitot Tubes

This is our open thread. Please feel free to offer your own comments.
The pitot tubes used on some Airbus products have entered the news again.  This time it is affecting probes made by Goodrich Corporation, based in Charlotte, North Carolina. These were the preferred replacement for the pitot tubes made by France’s Thales that were suspect in the crash of Air France flight 447 into the Atlantic Ocean. Here is a basic diagram of a pitot tube:

PitotTube.Ps, the static pressure, is derived from a series os small holes along the circumference of the pitot tube. The small holes reduce turbulence and provide a near perfect representation of the average air pressure of the environment.

Pt, the dynamic pressure, is derived from the head-on airflow and represents the air pressure felt from the forward motion of the airframe.
For those interested in the exact technical details of how this works, please go to the reference link from “pitot tubes” at the top of this thread. I will try to describe the issue at hand in layman’s terms. Otherwise, this thread would become a potential doctoral dissertation.

The ratio of the static versus the dynamic pressure along with a few algorithms (Engineers call these “Rules of thumb” which mean “I don’t know why this works, but it does.”) are used to determine the forward airspeed of the airframe. The automatic pilot is privy to the calculated airspeed. A problem arises when either or both of the input port systems are blocked by ice formation. If ice clogs both port systems, then the plane is assumed to be at a standstill. If the static ports are blocked, then it is assumed to be going forward a speed limited only by the degree of maximum deflection of the diaphragm. If the dynamic port is clogged, it is seemingly flying in reverse at a rapid pace. There are three pitot tubes per plane in order to allow for the failure of any one. If two or more fail, the autopilot is confused and relinquishes control of the plane. If the pilot and/or copilot fail to rectify the situation all on the airframe will buy the farm.

38 thoughts on “The Watering Hole: September 24 – Pitot Tubes

  1. Slight experiment here, to see how this works.

    ACORN Sues Creators of Sting Video

    “The liberal group contends that the audio portion of the video was obtained illegally because Maryland requires two-party consent to create sound recordings.”

    Barney Frank on The Factor about the Acorn Lawsuit

  2. Left-handed Underwear For Men

    “Hom, the company behind the pants, claim the underwear will “save left handed men up to three, often vital, seconds when visiting the loo”, potentially helping a raft of left-handed men, from American presidents George Bush, Bill Clinton and Barack Obama to Uri Geller and Paul McCartney.”

  3. Walt, every plane I flew (3) had a pitot tube heater that one turned on pretty much every trip so that ice would not form on the tube anywhere.

  4. Being a life-long lefty (physically and politically) I have trained myself to use my right hand in this situation. So saying, I can’t imagine using my left hand. It would seem unnatural. I have always said that righties would be in a world of hurt in a left-handed world. By the way, I agree on the kilt option. I love wearing them.

  5. TtT,
    The problem is at high altitudes, the heaters can not always deal with large quantities of super cold ice that can form in thunderheads.

  6. Hey Terry,
    what types of planes have you flown?–just curious

    (myself, I tried flying a spitfire once but it stalled as soon as I threw it and then the cat ran off with one of the wings.)

  7. TtT,
    Actually it’s supercooled water droplets which can suck up to 20 calories per gram from the heater system when they hit and require another 20 calories per half gram to remove when their initial state is -20 degrees C. Below -20 degrees, there is no liquid state of water. See this phase diagram.

    Update: I changed this comment as I did additional research after posting it. WTM

  8. House, I saw the pimp and girl on MSNBC this morning and anybody with half a brain could figure out they were phonies. My guess is the ACORN folks were just trying to get them out of the office.

    Anyhoo, the trolls are moving off ACORN and onto the Federal Reserve. They’ll probably be punking Bernanke next.

  9. Shayne,
    Did you see the link to the Huffpost story I put up on BnF’s post yesterday, about the anti-Acorn bill Boner is trying to get passed? Be sure and heed the warning to not be eating or drinking when you read it.

  10. totally off topic but any suggestions if you’ve got them.

    I just went to renew my CA drivers license and said they wouldn’t renew it because I have a ticket in MA from 25 years ago that wasn’t paid.

    Now I have to call MA and see where that get’s me. How do I prove I paid something 25 years ago? A little unreasonable, no?

  11. mikerush wrote: “I have always said that righties would be in a world of hurt in a left-handed world.”

    I’m a lefty. Long, long, the days ago, me and my ex husband added on a new kitchen and bath. I was left to deal with the contractor and his questions on where to put this, where to put that. The kitchen, and bath, was so left handed that my husband could not function in those two rooms at all. Everything opened to the left, light switches were on the left, bath faucets were on the left, etc. It was the only two rooms, in the world, that I couldn’t get hurt in.

  12. I’m old enough that when I was a kid they used to make you write with your right hand. No left handers allowed. I switched to writing with my left hand in the 7th grade and have been able switch hands ever since.

    Mostly I’m right handed, but I write with my left, eat with my left etc… Interesting when I took the left right brain test I could only see the dancer turning clockwise.

  13. whom,

    I’ve never been in a left handed room, it seems pretty interesting. They do say left handers are accident prone – could be because everythings made for righties.

  14. dananmao, I’m so left handed that I can write in script and/or print backwards as fast as I can write forwards, as well as take dictation (remember steno?) backwards from right to left. The only thing I do right handed is bat or play putt-putt (because my father taught me.) My lifetime motto is that my right hand is strictly ornamental.

  15. whom,

    That’s amazing. I thought I was a little unusual, but write/print backwards – that’s talent. Have you tried the brain test? They have it here, just search left right brain test and it will come up. I was dissapointed I could only see it turning one way.

    They also say premature babies are predominently left handed. That’s me.

  16. dayanmao, I took the left right brain creativity test as well as the other test to determine the direction in which the dancer is twirling. I see the dancer twirling clockwise (indicating right brain). In the creativity test, I score 31% left brain, 69% right brain. I’m hopelessly right-brained.

    Now, for shits and giggles, I showed my right-handed son the dancer. He easily sees her switching; going counter clockwise, as well as clockwise. I’m still searching for the counter-clockwise twirl.

  17. I was doing some bookkeepping and my son came into my room and played Ode To Joy, without his guitar being plugged in. Reminded me of a tune I just love from a movie, perhaps, you’ve heard of the movie. The Cowboys. (My favorite John Wayne flick.) There’s a scene where a kid (a young Revenge of the Nerds Carradine) is sitting at the campfire with his guitar and he’s plucking at the strings. A younger kid says “it’s pretty; did you write it”?. Carradine says “No, it’s written on paper.” Young kid says “it looks like fly specks”. Carradine says “there’s nothing to it; and it’s just just like arithmetic; you count the lines and spaces; tells your where the notes are; it ain’t hard. It’s kind of pretty, some guy named Vivaldi wrote it.” Played it for Connor and he’s going to learn how to play it for me.

    The song alone is worth the price of the movie. A gorgeous Vivaldi classical guitar solo to a magnificent view of young boys herding cattle in our 1880s midwest, with John Wayne in tow. (My bet is the guitar is a Martin or Taylor.)

  18. Didja ever notice of all the remakes that have popped up over the years, no one has ever done any remakes of John Wayne’s movies? Shoes too big to ever fill. I don’t think there’s an actor out there who could pull it off.

  19. “…FEMA had purchased thousands of trailers from Gulf Stream since 1992 without receiving any formaldehyde complaints until 2006.”

    So they COULDN’T have been built with cheaper, less safe materials at any time?

    Judge Kurt Engelhardt, the presiding judge, was a 2001 Bush appointee. Even though it was a jury verdict, the judge can easily steer a case to benefit the corporate interest. This case smells worse than the trailers. They are trying to avoid a class-action settlement.

  20. HoR, No. Don’t work in a mortuary. Not a HS Bio teacher either. It’s a play on… I love the smell of napalm in the morning…

    Me, I’m a six month unemployed tech writer left to doing anything to prevent from going insane due to mental inactivity… Cripes, I’ve even resorted to editing potential published poets on TP…

  21. whomisspoketoday,

    tech writer?

    Meaning writing technical instructions, process guides, user-guides that sort of thing?

    Because if that’s what you mean, a tip of the hat to you. I’ve been obliged in the past to write such stuff myself and it can be brutal if you care about what you are doing, about who is going to have to depend on your instructions.

  22. Zooey, I worked with manufactured sheet-stock for over 15 years, interior and exterior grade.
    I worked with quite a few industrial finishes/glues/sealers too.

    Once in while we’d get sheet stock that smelled (always from China, never from Canada) and we’d reject it not because we couldn’t deal with the smell but because it wasn’t SUPPOSED to smell–it wasn’t properly cured and there was some active chemistry going on.

    I once looked into buying a trailer home and checked a few out in Pennsylvania. They all smelled, and it wasn’t damp or mold or cigarette smoke.

    Without direct evidence, but through experience I have no doubt that the vast majority of FEMA trailer-homes are toxic–not “irritant”but seriously toxic.

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