This is a comparison of an F86 Pitot tube problem to a Boeing 737 with the same problem.
An air speed indication problem.
The Following Events took place in 1955 at Hahn AFB, Germany and relate to this comparison:
Upon take off, a new F-86 fighter’s instrument indicated a stall speed even when the aircraft was airborne. The fighter pilot at the controls was one of the best in the Air Force. He said he knew he had enough airspeed but was too low to nose Down to increase his air speed. To play it safe, he hit the afterburner and called the control tower
A Second F-86 was launched and flew next to the 1st F-86. Both landed safely. If the 1st F-86 Had crashed, we would have been unable to locate the cause of the low-speed indication, but fortunately we did. An instrument technician located the problem. It was OMG I don’t believe it!
It was like a needle in 1 million haystacks. Call it lucky or a blessing but it happened.
But how does this connect with the Boeing 737 problem?
Both aircraft we’re new and the problem occurred during takeoff, but One Major Difference between the aircraft became a game changer. The F 86 didn’t have a computer with a stall preventing system. But the 737 did. The F 86 auto pilot was off during takeoff.
The Boeing 737’s Computer responds to the input from the pitot tube output with lightning speed when a low speed indication is received.
While instrumentation was not my Area of responsibility, the pitot tube was connected to a small gyro computing device that was used to aid in computing the lead angle when firing the cannons. We had to disconnect the pitot tube from this gyro computing Device and reconnect the pitot tube after we completed testing this gyro Computer. It was my responsibility to make this reconnection so if the first F-86 had crashed, we would not have discovered the very small and loose connection of the pitot tube hose to the gyro computer.
To avoid the odds of this same problem recurring we implemented a double check off system. Two technicians were directed to sign off each time the hose was removed and replaced. A supervisor made one more inspection before a Final sign off was completed.
The problem never reoccurred again.
The Pitot tube hose was not tightened to the computer sufficiently to prevent leaking flow from occurring around the threads of the connector.
My conclusion is, the problem is a result of either a mechanical component defect, a component remove and replace maintenance mistake i.e. a loose connection, a leak in the pitot tube hose, a defect in the manufacture of the components used in the pitot system.
My suspicions that need to be investigated are,
Offshore manufactured components used in the Pitot System.
What is their QC procedure?
In view of my past challenge with the Pitot System,
There may be a simple solution.
But if we don’t follow on every possibility,
We must consider the consequences.
Robert J Bartol Jr.