Comparison of Flight Data Recorder
Information as Recorded On
Aloha Flight 243 Vs. FEAT B-2603
The thought process is thus:
A 737-200 flying at 300 kts has a rocket motor mounted vertically up at its
nose. With a high enough thrust, in a one second time frame, the aircraft could
be rotated exactly 90 such that the nose is pointed directly down. Since, in this
one second time frame, we have increased the cross-sectional area in the
direction of motion many fold, the entire aircraft is experiencing a HUGE
negative G reaction which is off the chart of the FDR. Now that we have
destroyed one 737, on the next test aircraft we mount a nose cone rocket motor
with only one half the thrust. On rocket motor burn, the thrust only forces the
nose down 45 . However, the rapid increase in cross-sectional area again
induces a large negative G recording. By varying the thrust, or with a constant
thrust rocket motor, varying the position along the longitudinal centerline, this
experiment should be able to reproduce on the FDR any value of negative G, at
will. Conversely, any value of positive G could be reproduced by facing the
rocket motor downward.
How this impacts the FEAT and Aloha accidents:
The air escaping from the ruptured fuselage is equivalent to the thrust
from our hypothetical rocket motor. Since the two subject aircraft are virtually
identical, the velocity and mass of the escaping air may be assumed equal and
providing equal thrust.
The accompanying drawings indicate the calculated center of explosion of
the FEAT aircraft based on the negative G reading recorded on the flight data
recorder. Furthermore, there was no indication of a defective accelerometer
which should have registered a large POSITIVE G indication had the failure
origin been in the lower lobe as reported.
The FEAT Report stated that the G force recorded on the flight data recorder
was "outside the flight characteristics of the aircraft". Since the airplane 'could not
possibly do that...' the investigators concluded therefore the data was erroneous and
ignored the flight data Gforce track data throughout the rest of the investigation. The
following diagrams show that an initial failure at BS504 on the S-4 Lap Joint would give
exactly the negative 4G swing about the center of gravity of the aircraft as recorded. It should
be noted that at the time of the Aloha accident in 1988, an FAA Airworthiness Directive was
in place requiring mandatory inspections of the S-4 Lap Joints BUT NOT the S-10 Lap
Joints.
