Originally Posted by
JRBarrett
If a pitot tube is completely blocked on the ground, and the barometric pressure falls substantially from what it was at the time the blockage occurred, the trapped pressure (compared to the still open static port), can cause the airspeed to show a positive reading. This happened once to me with a Gulfstream G200. The pitot tube cover was made of molded plastic and had no vent hole. Apparently it made a completely airtight seal when installed on the pilot side pitot tube. We installed the covers when bringing the aircraft into the hangar after a flight on a day when the barometric pressure was 30.45 in/hg. A few days later, I powered up the aircraft on the GPU to do a preflight maintenance check, when the barometric pressure was about 29.75 in/hg. I thought there was an ADC failure because the pilot airspeed was showing about 65 knots. It took a few minutes to figure out what was going on. After pulling the pitot cover off, the false airspeed reading disappeared. At least it proved that the pitot line from the tube to the ADC was completely leak free on that particular aircraft...
Good story! Yours was sealed up well, and this Abdul-Majeed Marouf Ahmed Alani nut-job used foam so didn't get a seal. Yet it would be enough to mess up total (ram air) pressure. Good thing the air crew was alert enough to abort the takeoff.
Wondering how a person with that record years ago got hired by American Airlines. No evidence he aligns himself with middle eastern lunatics here, yet his incompetence alone should have raised alarm bells. ..... I'll look for more and accurate news reporting on this subject, if somebody will cover it. For example, I still think it's bizarre how the sabotage happened in July, and obviously discovered, while it took over a month to arrest the crazy person.