B-908 CRASH OPERATIONS REPORT

• Document Type: FOIA
• Collection: FOIA Collection
• Document Number (FOIA) /ESDN (CREST): 02145427
• Release Decision: RIFPUB
• Original Classification: U
• Document Page Count: 5
• Document Creation Date: March 9, 2023
• Document Release Date: August 21, 2020
• Case Number: F-2015-00256

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B-908 Crash
Operations Report
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The CAA has concluded, in its "Salient Points of .rIvestigation Report on CAT's B-908
(C-46) Crash", dated 15 July 1964, that "based on the substantial wear and.tear of
left control cable And the uversr,eeding of left propeller ... normal time main-
tenance for the aircraft was not attontively carried out and ,.. there was also
indication of improper handling on the part of the pilot". The purpOse of this
report is to review the finding by CAA of "improper handling on the 'part of the
pilot", first.referring to the conclusion of CAT 's "Maintenance Report" and then
examining the general considerations of piloting an aircraft such as the C-46 tYPe,
explaining the training and checks of the pilots of B-908, and finally examining
the possibility of "improper handling" by the pilots.
CAT's "Maintenance Report" points out that CAA's finding that there was "substantial
wear and tear of left control cable and overspeeding of left propeller" is not
only contrary to available significant technical evidence of positive reliability
.and to the statements of eyewitnesses but also contrary to the reports of American
experts and laboratory analyses. The "Maintenance Report" also notes there is in
fact no evidence of any kind uncovered to date that there was any mechanical trouble
ef any nature at the time of the crash. If the "improper handling" found by CAA
refers to handling of the mechanical trouble reported as a finding by CAA, as it
see..;.s to by its context, then the conclusions of CATIs "Maintenance Report" alone
show a crucial fault in the reasoning used by CAA. Nevertheless, the possibility
of any manner of improper handling by the pilots, whether of the mechanical troubles
suggested by CAA or of other mechanical troubles or of handling of any other nature,
should be analyzed.
C-46 aircraft such as 13-908 incorporate dual provision of the equipment and controls
vital to the safety of the aircraft. The aircraft has dual sets of controls, which �
can be operated by either of the two pilots. Each set of controls further has dual
means of positioning the control surfaces of the aircraft. It has two engines,
although the aircraft can fly safely on one, and all cylinders of each engine, are
fired by two, separate, electrical sources. It has radio and navigation equipment
that provides several alternative means of communication and navigation under All
conceivable flying conditions. There are feur direct means (automatic or manual
control, feathering, and a brake) to control the blade angle of the propeller, and
hence propeller and engne speed. The hydraulic system has two enjne-driven pumps,
either of which is adequate to supply the system, and also has an auxiliary, hand)
pump to supply pressure where vital for operation of aircraft components. Aircraft
are unique in the extent of these and the other provisions made for safety in their
design and therefore cannot easily be compared with the equipment used in other
forms of trans-puitation.
Aircraft pilots belong to a highly specialized. profession. Professional pilots
should be emotionally stable, have excellent health and have been educated to a
standard which is considerably above average. Before a professional pilot can
begin training and periodically durin his career he must take rigid 7:,hysical
and mental examinations to insure that these qualifications are met. In the early
stages of training a professional pilot devotes most of his time to intensive
cuurses of study of aircraft and the technieue of flying. Such subjects as theory
of flight, power plants, meteorology, and navigation, in addition to the procedures
for flyin4 the first aircraft, are taught. The first aircraft the professional
pilot flies is a small propeller driven one; gradually, he will progress in his
career to piloting larger, multi-engined aircraft.
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Continuous study of aircraft and flying and the flight procedUres for particular
aircraft is necessary, for professional pilots to remain qualified to fly. Their �
qualifications are periodically checked by written examination and by observation
of their actual piloting of the aircraft under various simulated flight conditions.
Their knowlodge and performance of procedures to be used in such cases as engine
failure at takeoff and inf light, runaway or overspeed propeller, fuel system
failure, and emergency landing and evacuation is required to be correct. As the
aircraft take's off on these "check" flights the pilot being examined must, for
example, know the procedure for safe handling of engine failure so well that he can
execute it without a moment's hesitation when the "check" pilot suddenly pulls back
the throttle of an engine just at a critical point of takeoff.
Both Bengee Lin, the pilot-in-command of .B-908, and M. H. Kung, the second-in-command
of B-9081 were selected, trained and qualified as professional pilots in the manner
which has been described. Bengee Lin had flown 11,881 hours, of which 4,914 hours
was flown in the C-46 type aircraft. M. H. Kung had flown 13,074 hours, of which
at least 9,270 hours was flown in the .C-46 type aircraft. Bengee Lin had 17 years
of experience as a professional pilot. M. H. Kung had 19 years of experience as a
professional pilot. The results Of their most recent periodic physical examinations,
their duty records, and the observations of their co-workers up to their departure
on their last flight indicate both were in excellent physical condition and were -
neither tired nor emotionally disturbed.
Bengee Lin and M. H. Kung were so experienced that it was second nature for them to
keep an airplane in the air or land safely in the event of malfunctions such as an
overspeeding propeller or broken control cable. If such a malfunction occurred each
and both would be expected to immediately react and counter the malfunction almost
subconsciously.
The CAA report, however, finds that "there was indication of improper handling
on the part of the pilot. To examine the possibility of "improper handling on the
part of the pilot" causing the crash, it is necessary to trace the course of B-908
just prior to the crash. The aircraft had taken off south from Sui Nan Airfield and
turned to the left 1800 to proceed north to Taipei. beveral competent witnesses
observed the takeoff and initial climb and stated that the aircraft behaved normally.
The Control Tower operator watched the aircraft until it passed to
the northeast of the airfield at which time one of the pilots called the tower and
advised they were climbing on course and would see them tomorrow; the operator
observed that everything was normal. A number of ground witnesses saw the aircraft
as it approached Feng Yuan, which is north of Taichung. The consensus of reports
by these witnesses is that the aircraft was travelling to the north when it suddenly
made a sharp turn to the west and started to descend at a rapid rate from an altitude
of 1200/1500 feet, based.on the time from takeoff and statements of witnesses.
Within 20 to 30 seconds it hit the ground at about a 300 angle with the left wing low.
Assuming this crash is believed by CAA to be the result of "improper handling" of an
overspeeding propeller it has not been explained in what respect both pilots failed
to properly execute the procedures prescribed. An overspeeding propeller does not
of itself have a substantial effect upon the performance of the aircraft. The air-
craft would continue, on course, while either pilot executes the prescribed pro-
cedures. Since the phenomenon of an overspeeding propeller is much more crucial in
the takeoff regime and is manageaole under such circumstances, had it occurred at
the comfortable altitude and flight regime of B-908 it would be little cause for
concern.
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Ample evidence is available to demonstrate the measure of control of propeller speed
available to the pilots. In one case observed by several competent witnesses the
left propeller of a C-46 began overspeeding at an altitude of only 200 feet shortly
after takeoff and while the highest engine power was being utilized. The pilot
simply retarded the throttle on this engine and the RPM immediately came down to
within the allowable range. There was no change of course or altitude during this
condition.
The great dancer of an overspeeding propeller is not that it will upset the aircraft
performance but rather that the propeller or its engine will be unable to withstand
the higher than designed for stresses generated by the higher rotational or recipro-
cating speeds involved and so the propeller may fail, throwing parts into the vitals
of the aircraft or, having become unbalanced by loss of .a part, wring itself or its
engine from the aircraft -- or the engine may come apart or seize possibly resulting
in the propeller being thrown off or a fire started. Since it has been established
by various investigators, including the CAA, that none of these things, which could
result from.improper handling by the pilots, happened to B-908, there then is no
evidence to support a conclusion that "improper 'handling", had there been the pro-
peller overspeed reported as a finding by 'CAA, caused the crash.
Assuming the crash is believed by CAA to be the result of "impror.er handling" of a
broken or worn elevator trim tab control cable it has not been explained in what
respect both pilots failed to execute the procedures prescribed. Even the sudden
severence of one of the two cables controlling this control surface of the aircraft
has only negligible effect on its 1:iosition. The control surface could still be
operated in one direction. In actual flight tests with both elevator trim tabs in
the positions required for the extreme nose-up or nose-down attitude Of the aircraft,
simulating the most adverse consequences of elevator trim tab control cable breakage
or wear, a pilot was able to control the aircraft easily without any deviation in -
course or change of altitude with only one hand on the yoke (which provides an
auxiliary means of direct control of the pcsitinn of the elevators). This evidence .
sharply contradicts any conclusion that "improper handling", had there been the wear!
or breakage of an elevator trim tab control cable prior to the crash as reported as
a finding by CAA, caused the crash.
The stall characteristics of a C-46 aircraft are excellent under all conditions.
The steep angle of descent along a relatively straight line provides ample evidence
that the aircraft speed was far above the stalling speed and that there was no stall
prior to the crash, and therefore also no improper handling in this respect by the
pilots.
since the seat of Bengee Lin, the pilot-in-command, was shattered into several pieces
by the crash, it is not possible to state with any degree of accuracy whether he was
strapped into his seat by the safety belt at the time of impact. . It was his known
habit to fasten the seat belt, however, so there is no basis for any conclusion
that it was not' fastened and consequently .no basis for any conclusion that Bengee
Lin was over confident or negligent. A signed statement by the CAT authorities who ,
have been improperly quoted in this matter is attached.
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The CAA finding of "improper handling on the part of the pilot" then is not supported
by any evidence of mechanical trouble which would require special handling, as the QAT
"Maintenance Report" concluded. The CAA finding is also contrary to the factual '
details of the path of the aircraft, to the plausible reactions of both pilots, to
the high qualifications and long experience of both pilots and to even CAAls findings
of mechanical trouble. It is difficult to conceive what the pilots might have done,
or failed to do, that would have resulted in the strange behavior and flight pattern
of the aircraft after the normal departure from Taichung. The weight of evidence
available to this time indicates strongly that the aircraft was intact, was func-
tioning normally and was controllable up to the moment of impact. The settings of
cockpit controls examined soon after the crash and during subsequent investigations
showed no inf light mechanical emergency against which countermeasures had been taken'
and no preparation for an emergency landing, although the pilots were fully qualified
and capable of making an emergency landing had it been required.
The flight -pattern and absence of the typical immediate announcement by radio of
mechanical difficulty strongly suggests the incapacitation or restraint of both
pilots rather than improper handling on the part of the pilot or malfunctioning of
the aircraft. In this light the CAA conclusion that the pilot, who epitomized the
highest standard of his profession and was a credit to his nation, was guilty of
improper handling is a bitter irony as well as a gross injustice.
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Attachment to Olperations Rel:)ort
STATMENT
Re: Control Yuan Investigation Report
"Mr. D. Teeters and Mr. D. Gluskin told us that Lints remains were placed three
meters from the pilot seat and his safety belt was still left on theseat.
This indicates that Lin didn't fasten his belt before takeoff; otherwise the
belt, if not broken, should have been found wrapped around Lin 's body. Basing
upon this, we can judge that Lin was over confident and negligent."
The above paragraph would have it appear that the Control Yuan members were
responsible only for the last sentence and that we (Teeters and Gluskin) made
the observation that the seat belt was not fastened. This is an incorrect
assumption and we believe it needs clarification and correction.
The question asked was whether Capt.
reply was substantially as follows:
Lin's body was found in his seat.
Our
The body was found approximately 10 feet from the center of the general area
of the cockpit wreckage. since the seat was completely destroyed and in several
pieces it was impossible to state with any degree of accuracy whether at the
time of impact Capt. Lin had been strapped in his seat.
It is of vital interest to all concerned that statements not be quoted out of
context nor so altered as to destroy their validity.
Khile on the subject of safety belts, it is the custom of pilots to keep their
safety belts fastened while flying. It was a known habit of Capt. Lin to do
this, and there is no basis for any supposition that his safety belt was not
fastened at the time of the crash.
s/ David B. Gluskin s/ Donald E, Teeters
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