View Full Version : B767 Airspeed loss ATO
Im trying to remember what caused this.
It only happened to me once taking off out of DXB.
The autopilot was engaged, therefore as I recall VNAV had been selected. The airspeed reduced. I cannot recall where the Airspeed CMD bug was.
It required pilot input to stop the airspeed reducing.
Any pilot or Sim instructor can explain what the situation was?
RohanThePilot
28th Mar 2012, 09:20
Hi Soab. Sometime ago, I was observing a similar prob on the 757 as well. AP & VNAV were engaged and we were climbing thru FL230 when the FMS acted as if it was not bothered about IAS. Pitch was remaining constant and on the ASI speed was dropping. The Capt. switched to FL CH mode and then things became OK. After a while VNAV was engaged again and then things were normal. Crew were quite unsure of what caused this.
I personally feel that the 57 and 67's VNAVs are a little sloppy at times...
This was a very specific issue. AP & VNAV were engaged, it was just after takeoff but after Flap retract, yet speed reducing.
I talked to a SIM instructor on my next SIM and we tried to simulate the scenario. He did give an explaination, but it wasnt that clear, thus I cannot remember.
I am not flying the B767 now, so cannot quiz the other crews or SIM Instructors. (Id say it only very occasionally occurs in the aircraft, so SIM instructors may not have experienced it in the SIM) Only happened to me once in over 10 years on the Airplane.