The long takeoff roll still seems highly signifigant,
being the first clear indication of a problem.
1) Could an issue with the ram air temperature transducer
whose output signal is necessary for the accurate calculation
of EPR, have led to a falsely high reading of actual takeoff EPR and hence giving a lower than indicated actual takeoff thrust?
2) Could an issue with the air/ground sensing equipment
have had an affect on the airplanes allowable EPR
and hence thrust on takeoff?
(eg. arent there different epr limits for each flight mode ?)
There have been cases in the past for example air florida flight 90 disaster
where falsely high EPR indications caused by faulty / contaminated sensors (in this case ice) led to the pilots experiencing insufficient thrust and stalling on takeoff despite
apparently normal epr and thrust readings:
As it turned out, the failure to operate the plane's anti-icing system caused exactly what could be expected to happen: the engine pressure ratio (EPR) thrust indicators provided false high readings — when the pilots thought they had throttled up to the correct take-off EPR of 2.04, the actual EPR was only 1.70. The aircraft traveled almost ½ mile (800 m) further down the runway than is customary before liftoff was accomplished.
full version:
Air Florida Flight 90 - Wikipedia, the free encyclopedia
Although this was a 737 and the EPR values
were distorted by an ice contaminated sensor,
it shows how critical it is for sensors
such as the RAT probe to be functioning correctly.
Inadequate thrust of the airplane would explain the long takeoff roll
(extra 500m)
A symptomatic RAT probe and an airplane that doesnt know if its on the ground or in the air could easily lead to false EPR values and hence lower than indicated takeoff thrust.
Despite reaching vr it is possible the airplane
had not sufficient thrust
to takeoff without stalling.
possible ? il leave it to the experts