Changing airspeed?

MLock · #1 10-04-2012, 04:37 PM

This past Sunday, while on the way home from a local flyin in Winchester, Va., I was cruising along at 2,000 feet with an indicated airspeed of 109 KTS at 5400 RPM. All of a sudden, my IAS drops to 64 KTS. Quite a surprise since I hadn't reduced power and wasn't climbing. Groundspeed remained the same. Hmm? What's going on here? The day was crystal clear with almost no wind and home was only 30 miles away. So for the last few minutes of the flight I wondered what was up. Something must have happened to my pitot system. Either there was a big leak in it all of a sudden, or it had become clogged.
Once back in the hanger, I looked at the pitot tube. Nothing apparent. I then stuck a piece of piano hinge wire in it and it stopped about six inches in. I removed the top cowl, disconnected the hose and pushed on the wire. Out came the remains of some sort of insect. Now what are the odds of me taking a bug down the pitot tube in flight?

Bill_H · #2 10-04-2012, 04:48 PM

9,000 foot altitude in a Mooney returning from Oshkosh way back in 1991. HUGE bug of some kind splats on the windshield. Didn't think they went that high.

krwalsh · #3 10-04-2012, 05:11 PM

The probability that you would get a bug in your pitot tube, on this particular flight, is 1.

Sorry, statistics geek humor. I've been crunching numbers in a stats program for the past two weeks, and just had to let that one go.

http://xkcd.com/552/

NASA515 · #4 10-05-2012, 12:29 PM

The odds in your case - on that flight - were 100%, Mitch.

Glad you carried on without problems - better than a number of air carrier heavy metal drivers who lost their airspeed indications and then lost their airplanes.

Bob Bogash
N737G

RDOG · #5 10-05-2012, 03:39 PM

Beware the Rain!

RFSchaller · #6 10-05-2012, 09:21 PM

More probable is that it built its nest while in your hangar and the nest was disturbed by airflow causing it to block the tube. Bugs seem to love the geometry of probe tubes. I had the same thing happen on my Searey, but I never got an airspeed indication on my takeoff roll.

BobTurner · #7 10-05-2012, 10:53 PM

My former partner in a 182 hit a bug just after rotation from Johnson Creek, airspeed went to zero.

6S4 Hugo · #8 10-07-2012, 07:46 AM

Quote:

Originally Posted by Bill_H

9,000 foot altitude in a Mooney returning from Oshkosh way back in 1991. HUGE bug of some kind splats on the windshield. Didn't think they went that high.

http://www.npr.org/player/v2/mediaPl...87&m=128532096

"In Berenbaum's article, she mentions a 1961 study by J.L. Gressit in which an insect trap was placed on a Super-Constellation airplane. That plane flew 116,684 miles sampling the air, catching whatever was up there, and, Berenbaum says, "the trap managed to capture a single termite at 19,000 feet." That's the record."