| Maintenance
How well were the HP42's maintained?(13) Much of the attitude toward
maintenance seems to have been as much by experience as by schedule. These were
still early days in aviation and the type of rigid maintenance schedules imposed
by experience and accident investigation were still to come. Metal fatigue as
applied to airframes- a young science. This has been suggested by other documents in the PRO.(13)
PRO records covering maintenance and the accident investigation suggest
some straight forward explanations for the loss of Hannibal.
1. AVIA5/13 (section 18) - Describes a crash the
Hannibal had early on in its life. A single engine failed followed
by the failure of one of the other engines. The aircraft made a
forced landing in a field. Most of the damage to the Hannibal was
sustained when it hit obstacles in the field. None of the
passengers or crew were hurt.
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Added 02/2018
An event in Palestine in November 1932 adds to airframe stress
considerations. Here.
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2. AVIA2/892 - Maintenance records from Heliopolis where the
HP42 eastern types were based. This contains a memo concerning the
maintenance schedules of the HP42 aircraft (Dated 19/9/35). It
makes 2 main points:
a) Due to the age (5
yrs?) of
the HP42 aircraft either they need a total strip down or their
routine maintenance schedules need to be carried out more
thoroughly.
b) Imperial Airways
will only do the absolute minimum to keep the aircraft in the air
(and gives an example).
Note. “Captain Townsend and the other
HP42 pilots were increasingly concerned about the age and vibrations
on the HP42 fleet.” (57)
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3. AVIA 2/2311 - The accident report concludes the most likely
reason for the loss was multiple engine failure causing the
aeroplane to descend into the sea shortly after the last
transmission. The last transmission broke up due to the trailing
antenna wire touching the surface of the sea. The report goes into
great detail describing the possible mechanical failures but
suggests the failure of one engine could lead to one or more of
the others failing due to increased stress. The Hannibal
could fly on 3 engines but would be forced to slowly descend on 2
engines. (Note: an HP42 made the trip from Croydon to Paris on 3
engines to demonstrate the reliability of the aircraft.)
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This last point is very dependant on the actual flying
altitude reported/recorded in the radio log. It seems improbable that 100
ft is a sensible altitude for a proposed over water flight. It gives no
margin for error should even one engine fail. Radio aerials trailing
behind risk touching the water or any vessels encountered enroute.
Although the Dibba- Sharjah pass through the mountains is comparatively
low in altitude, it would require a climb from 100ft. 1000ft
allows a greater safety margin. (The Hajar Mountains rise to 6800 feet. to
the north of this route.) This would discount the
accident investigation report's theory on the failing last transmission,
unless only the last transmission of a series was recorded. An overloaded airframe may have been stressed to failure and subject to
declining lift as the days temperature increased.
AVIA
2 /2311 – It seen in the official report that, “As a result of
pilot's remarks of poor performance the aircraft” (G-AAGX) “
was taken off service” on 10.7.39 – “AND REMAINED IN STORE
AT ALEXANDRIA UNTIL 17.10.39.” Was demand for airframes such
that it was reinstated to service? However, “various and
continuous problems “ were “reported including engine failure
, vibration and poor climb rate.” Also noted was, “Airscrews
changed on 4.12.39”, followed by “Further continuous
complaints of vibration and fuel flow problems”. Maintenance
concessions were extensive. One of these covering numerous flying
surface and control components expired or was issued at 11.30a.m.
on 2.3.40 whilst the aircraft was expected to be enroute to
Alexandria. A concession was made in extending one of G-AAGX’s
engines running hours from 600 to 625 hours on 25.2.40 (13a)
What engines and airscrews were installed on G-AAGX when
returned to service? The Jupiter XI F serial numbers installed are
in the official report. Some of these questions might be answered
by the rumoured existence of a photograph taken at Jiwani on the
day of the last flight. |
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