FlightGlobal.com
Home
Premium
Archive
Video
Images
Forum
Atlas
Blogs
Jobs
Shop
RSS
Email Newsletters
You are in:
Home
Aviation History
1925
1925 - 0084.PDF
FEBRUARY 12, 1925 which it left the ground. There is some divergence of view as to the courseof the aircraft, but, in my view, only in unimportant respects. It is established to my satisfaction that after pursuing a course in a direction more or less eastof south which took it over the railway which passes through Purley, it turned and followed a course in a direction more or less west of north. Ihave had the opportunity of seeing from a very good view point the country over which it passed. I am convinced that the turn was taken with theobject of landing. I have also come to the conclusion that a height was reached which, if all had continued to go well, would have permitted the aircraft tocontinue on its way ; but that from or shortly before the turn it lost height, until when over the place where it crashed, it was about 100 ft. above theground. The dive to earth was due to loss of control combined with a stall. That something went wrong is certain, but it is impossible to say whether itwas the engine, its installation, or some other part of the aircraft. I think that whatever was wrong caused the machine to lose height, or induced thepilot to descend at least from the turn onwards. There was no defect in the lubrication. The engine was carefully examined after the accident and notonly was nothing found suggesting that the lubrication had become in any way defective but everything pointed to its being in perfect order. Theignition system, namely, magnetos, and wiring, was practically destroyed by the fire which ensued on the crash of the machine, but it was possible todetermine that all the wires had been connected in their proper order and proper place. Only three of the sparking plugs failed to work satisfactorily onteat, and as to these, there is good ground for the view put forward in the evidence that this failure was due to injury after the accident. CaptainStewart had not put out the aerial of the machine ; and it was suggested that it might be he was unable to do so, and that this had caused him to returntowards the aerodrome. Even assuming that a pilot would put out his aerial so soon, this suggestion takes no account of the loss of height nor of theparticular turn taken. For some time the investigation seemed to point to the supply of petrol tothe carburettor serving the four cylinders on the starboard side having become obstructed by reason of the gilt lining of the petro-flex tubing between suchcarburettor and the filter becoming swollen with water and displaced. A portion of this tubing was found after the accident, and Major Cooper'sexamination of the same disclosed the fact that just about the lowest point of the bend of this pipe it was practically completely blocked for a length ofseveral inches. I am, however, convinced from the experiments which have been carried out. of which I have had evidence, that water cannot produceany substantial swelling of the gut, but that if the petro-flex piping is subjected to heat, as was the case when the fire ensued after the machine crashed, thegut lining comes away from the canvas backing to which it is glued, and shrivels, and that the pipe becomes similarly blocked. Accordingly, failurein the petrol supply due to the obstruction in this pipe, which was discussed Sitter the accident, which for a time seemed as if it might be the explanation,must be rejected as a possible cause. The blocking of this pipe found by Major Cooper occurred after and not before the accident. I may add that thebore of this pipe was ample to give a full supply of petrol for the four cylinders which it served. It has transpired in the evidence that on December 6, 1923, the Petro-Flex Tubing Co., Ltd., the only manufacturers of the tubing referred to in the last preceding paragraph, received from the Research Department of theAir Ministry an intimation that internally-wired petro-fiex piping in long lengths was approved for civil aircraft, and should in future be suppliedunless otherwise specified. This fact was not brought to the notice of the officials of the Air Ministry responsible for the inspection of aircraft prior tothe issue of the certificate of airworthiness, and at the time of the inspection in November, 1924, when the piece of piping above referred to was fitted orput back, which, in fact, was not internally wired, the officials conducting such inspection were unaware of the conclusion reached in December, 1923,by the Research Department of the Air Ministry. I refer to this matter only to recommend that this conclusion should be made known to the appropriateofficials of the Air Ministry in order that its application may be made certain in the future. It is right that I should add that the Petro'-Flex Tubing Co.,Ltd., have in every case since receipt of the letter of December 6, 1923, con- formed strictly to its terms, and, further, that Imperial Airways, Ltd.,were also unaware of the conclusion of the Research Department of the Air Ministry, and possibly when the machine was overhauled in November,1924, only put back the same piece of tubing which had served in the same position before the engine was dismantled. I find as a fact that there is noground for thinking that the absence of internal wiring in this piece of tubing was responsible for or contributed to the accident.There was some cross-examination, but no evidence led to show that on the occasion of the accident the maximum authorised weight had been exceeded.I find that this was not so, and that the total weight was about 7,160 lbs., or some 40 lbs. below the maximum authorised. Evidence has been given before me that the aerodrome at Croydon,especially with a south-west wind, is far from satisfactory. Colonel Edwards, the deputy director- of air transport at the Air Ministry, has given detailedevidence of the steps which the Air Ministry propose by way of improving this aerodrome. It is proposed to add substantially to its present area, theadditional land having been already acquired, and in order to make the land which has been acquired to the west available as part of the aerodrome,to divert Plough Lane, for which purpose a Bill is being prepared. These proposals are in general agreement with the suggestions for improving theaerodrome, made by the witnesses who gave evidence before me as to its unsatisfactory character. When Captain Stewart started, the wind wasfrom south south-west and the day pretty rough, and although the unsatis- factory character of the aerodrome was not the primary cause of theaccident, nevertheless it may have been to some extent responsible for its fatal result through the aircraft being lower than it otherwise might havebeen when the pilot found himself in difficulty. The evidence as to what normally occurs with the wind from the south-west when an aircrzft leaves the aerodrome at Croydon calls for some con- sideration. If it takes off upwind, the run on the ground is uphill, and aftertaking the air the aircraft has to surmount a hill rising in all to some 140 ft. above the starting point, and distant some 5,000 ft. therefrom. The crestof this hill is occupied in places by houses, rising, say, a further 40 it. The evidence establishes that it is by no means unusual for aircraft, taking offin these circumstances, to be unable to pass at a safe height over the houses. Accordingly, the pilot has either to make a fairly sharp turn soon afterleaving the ground, and this in breach of Paragraph 37 of Schedule IV of the Air Navigation (Consolidation) Order, 1923, or to take off across wind ; eachof these alternatives is undesirable. The evidence further shows that the margin of height at which aircraft pass over the portion of the crest of thehill which is unobstructed by houses is frequently very small ; for example, in the case of type D.H.34, fully loaded, 50 ft., although under favourableconditions greater heights are attained. The aircraft G-EBBX is estimated to have been from 50 ft. to 100 ft. above the crest of the hill on December 24,and Captain Barnard, who estimated the height to have been 100 ft. above, said the machine had climbed " quite remarkably well." It was given inevidence that other types of machine have been observed to clear the. crest of the hill with a margin even smaller than 50 ft. In view of thesr facts, th>-suflieiency of the angle of climb of aircraft habitually using the aerodrome at Croydon requires, in my opinion, further consideration, notwithstandingthe contemplated alterations to that aerodrome. The accident was attended with loss of life, because the aircraft made aspinning nose-disc from a height of about a hundred feet and struck the ground end-on at a comparatively high speed. The fact that the aircraftdived points to loss of control, due to its speed having fallen to the danger- point. It must be evident that every endeavour should be made to freeaircraft carrying passengers from this type of loss of control. A pilot normally retains a s peed considerably in excess of the stalling speed until the aircrafthas been brought down to a very few feet above the ground, after which ho keeps close above the ground whilst the speed is falling to the stalling speed ;on stalling, the aircraft sinks to the ground and then runs along until it stops. The distance covered whilst flying close above the ground is a sub-stantial part of the unobstructed space required for landing. In the case of a forced landing where the available landing area is small, the pilot is facedwith the danger of a serious crash in his endeavour to reduce speed sufficiently. Other things being equal, the higher the stalling speed the greater the diffi-culty of making a forced landing on a small area without an accident. The type D.H.34 has an exceptionally high stalling speed, viz., 62 to 63 miles anhour. This type has, however, exceptional qualities in the matter of the short distance in which it stops after sinking to the ground, and in respectof its controllability at speeds slightly above the stalling speed. Each ol these qualities offsets, in some measure, the adverse effect of the exceptionallyhigh stalling speed. The accident, however, was rendered fatal by just such a loss of control as would follow upon a pilot reducing speed in the air tothe danger-point. These considerations induce me to recommend that the Air Ministry should consider whether a limit should be fixed for the stallingspeed of aircraft carrying passengers. A point has been discussed before me, which in the circumstances is one ofminor importance, as to the true meaning of paragraph 8 of Schedule II of the Air Navigation (Consolidation) Order, 1923. It has been submitted thatMr. Hmchliffe having landed at Lympne on December Ti, the aircraft and its instruments should have been inspected there on the 24th, before theflight from Lynipue tn Croydon. The argument is not devoid of substance. as, the word " flight " in the paragraph not being defined, there is someconsequent ambiguity, and I suggest that it is desirable to consider the advisability oi re drafting this paragraph, or otherwise making clear tiremeaning of the word " flight " therein. It may be convenient that I should summarise the main conclusion;, towhich I have come : — (1) No official of the Air Ministry, or of Imperial Airways, Ltd., was inany way negligent in the discharge of his duties in relation to the aircraft G-EBBX. (2) Capt. Stewart was a skilful and experienced pilot, and no blame isattributable to him. (3) The dive to earth was due to loss of control combined with a stall,which occurred whilst the pilot was endeavouring to make a forced landing in circumstances of great difficulty.(4) The flight of the aircraft for about half the time it was in the air was normal. Thereafter some defect developed, but whether in the cnginr orits installation, or otherwise in the aircraft, there is nothing to show. (5) The aerodrome at Croydon is unsatisfactory. This was not the primarycause of the accident, and I do not say more than that it may have been a contributory cause.(6) The total weight of the aircraft on its last flight was less by about 40 1b. than the maximum authorised.(7) The Air Ministry should consider the question whether any and what limit should be fixed for the angle of climb, as also for the stalling speed, ofaircraft carrying passengers. (8) Every' endeavour should be made to free aircraft carrying passengers from the danger of loss of control associated with stalling. The Court does not make any order as to costs. (Signed) ARTHI'K COLEFAX. (Signed) B. MEI.VII.L JONES (Signed) J. SWINBURNE. THE CROYDON DISASTER INQUIRY THE Official Public Inquiry into the air disaster which took place at Croydon on December 24 was concluded last •week at the Law Courts before Sir Arthur Colefax, the Chairman, and two assessors, Prof. B, M. Jones and Mr. J. Swinburne, F.R.S., M.Inst.E. The fifth sitting of the inquiry was resumed on January 29, when most of the evidence given was of a technical character. Mr. Mervyn Henry, traffic clerk at Croydon, was the first to give evidence, and he repeated the statement he made at the inquest in respect to overhearing Capt. Hinchliffe complain of the engine. Mr. G. W. Glasson, who directed the traffic in and out of Croydon by wireless, stated that he thought the flight of the machine G-EBBX when it started on the fatal flight was not quite normal. He further stated that soon after Capt. Barnard left (just after the accident) he received a message from that pilot reporting that the down draught over the ridge at Hill Crest was very severe, and asking would Imperial Airways load their machines lightly. Colonel Frank Searle, Managing Director of Imperial Airways, described the system employed for the maintenance of aero engines and plant of the Imperial Airways. He said he considered the system adopted by them was better than any he had seen in other countries. As regards the Petro-Flex tubing, he said that they had done one and a-half million miles with this tubing without discovering a single defect. The presence of the unarmoured piece of 84
Sign up to
Flight Digital Magazine
Flight Print Magazine
Airline Business Magazine
E-newsletters
RSS
Events
