Further to previous posts. It is fascinating to read the often expert and not so expert opinions as to causes of accidents. Speculation on Pprune is healthy especially as it may reveal avenues of investigation that may not have been considered by the investigators involved. Some of us flying similar types in similar conditions may secretly think "There but for the Grace of God, go I"
The RNZAF Hastings crash discussed in previous posts here has always intrigued me because in another era, I dabbled in several military aircraft accidents in an official capacity. In the last few weeks, I was able through the kind efforts of people in the New Zealand Department of Defence, to obtain a copy of the Court of Inquiry on the Hastings accident. The cause of the accident could not be firmly established since in those days of 1955 there were no CVR or FDR's. So the Court of Inquiry was forced to speculate on the evidence available (reminds me of Pprune!)
Anyway, I thought Pprune readers may be interested in my brief summation from the pages of the Court of Inquiry. (I haven't read every page yet but enough to see why the Court of Inquiry were unable to pin down the specific cause of the prang.
Here goes:
The RNZAF Hastings took off from Darwin to go to Amberley. It had just got airborne and gear selected up when it had multiple bird strikes. A witness said he saw about 12 hawks on the runway. The crew felt a big bang on the nose of the aircraft. There was no swing. At least one bird hit the nose.
Almost immediately three engines lost partial power and with a rapid drop in IAS the captain made the instantaneous decision to throw it back from 100 ft wheels already up, on the remaining runway length. The aircraft slid off the end of the runway towards an embankment next to the main water pipe supply line to Darwin. To avoid colliding with the water pipe the captain applied full left rudder as the Hastings it slid on its belly and ground looped before hitting the pipe line with the starboard wing tip. Everyone got out unhurt (all passengers were sitting in backward facing seats) which was amazing. The aircraft did not catch fire.
The Court of Inquiry centred on why three engines lost partial power when no birds were found in the engine intakes. In those days British aircraft (including the Lincoln that I used to fly) had inertia switches that when operated by deceleration forces, automatically actuated the engine fire extinguishers. In the Hastings this inertia switch was in the nose and covered with a Perspex cover. Each engine on the Hastings had three fire bottles. It was found that in three engines some of the extinguishers had operated, while in the No 4 engine which never lost power, the fire bottles had not actuated.
The normal take of RPM on the engines was 2800. At the instant of bird strike it was seen that three engines momentarily dropped to 2200RPM - a power reduction which may have accounted for the IAS dropping from 125 knots at bird strike to 113 knots when the captain made the decision to throw it back on the remaining runway.
It was thought that birds hitting the nose of the Hastings might have actuated the inertia switch - although the plastic cover was intact when they found it later. Black smoke was seem coming from the engine exhausts shortly after bird impact. There was a thought that the FE might have loosened the pitch levers friction nut in preparation for reducing to climb power which is done when 125 knots safety speed is reached. Tests proved if that happens (friction nut loose) the pitch levers will slip back with momentary loss in RPM unless the FE keeps his hands on the pitch levers.
Later tests revealed that if the pitch levers drop back several hundred RPM with engines at full power, the exhausts emit black smoke. This does not happen if the throttles are pulled back.
The Inquiry had several theories to go on for the cause of the partial failures of the three engines. In the end these were narrowed to two possibilities. One was the pitch levers slipped back exactly at the same time as the bird strike. Secondly the possibility the nose bird strike actuated the inertia switch causing extinguishers to operate into the engines causing partial power loss.
The Inquiry stated the captain made the right decision when faced with significant loss of power on two out of three engines with a smaller power loss on a third engine and no power loss on the fourth. This was at max weight take off. The captain was also faced with the immediate loss of air speed at such a low altitude coupled with the fear the engines may not pick up immediately after they had failed.
Beyond the over-run area was the water pipe line, a railway embankment and trees. A forced landing further ahead among the trees could have proved fatal. So he made the decision to belly land it straight ahead on the remaining length of runway before it was too late. It was one of those once in a lifetime lightning quick decisions we all hope would never be required of us.
During the Inquiry he was asked if he had ever had an accident before. He replied that in 1946 he was flying a Liberator four engine bomber over mountains in Europe when he lost two engines. The Lib could not maintain height and he managed to force land it next to a road. The captain had over 5000 hours of which 1400 hours were in command on Hastings.
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Further to the above. Have just read Flypast magazine May 2013 issue. There was a fascinating article on Shorts Stirlings used in the civilian role.
A Captain Tam Morrison was flying a Stirling OO-XAC-on 21 December, 1947 departing Calcutta for Kunming.
From the article: "After pre-flight planning, Tam's crew and passengers boarded OO-XAC the following morning for the penultimate leg to Canton. Immediately after take off, at about 150-200ft, three engines failed leaving Tam no option but to put the fully laden aircraft straight ahead. Part of the path the aircraft took was through a cemetery of stone burial mounds. Each was about 4ft high, and these tore through the Stirling.
When it finally came to rest, the fuselage was largely intact save for the nose and cockpit. Tragically, the co-pilot died and the flight engineer suffered a broken hip, but thanks to Tam's skill the rest of the crew and passengers suffered only minor injuries. Such a catastrophic multi-engine failure suggests fuel contamination."
The report makes no mention of the possibility of a bird strike. But if there had been a bird strike and if the Stirling was fitted with inertia switches that actuated engine fire extinguishers, the circumstances would have been eerily similar to the crash of the RNZAF Hastings at Darwin eight years later.
Last edited by Centaurus; 13th Jun 2013 at 08:00.