FlightGlobal.com
Home
Premium
Archive
Video
Images
Forum
Atlas
Blogs
Jobs
Shop
RSS
Email Newsletters
You are in:
Home
Aviation History
1956
1956 - 0390.PDF
388 FLIGHT, 6 April 1956 D.H.9 modified tot night flying, with long "pepper-pot" exhaust-pipe to act as a flame-damper and silencer. THE DE HAVILLAND D.H.9 ... section, separated from his observer by the main fuel tanks, whichwere installed between the cockpits. On the D.H.9, however, the engine was only partly cowled: above the blunt cowling thecylinder heads and exhaust manifold were completely exposed. The radiator was mounted in the ventral position, immediately infront of the undercarriage legs, and was retractable: it moved vertically, and was actuated by a simple rack-and-pinionmechanism which was connected by an endless cable to a hand- wheel on the starboard side of the pilot's cockpit. The pilot sat behind the wings, and he and the observer wereclose together. The main fuel tank was installed immediately behind the engine. Between this tank and the pilot's cockpit therewas an internal bomb-bay which could accommodate two 230-lb bombs or an equivalent weight of smaller bombs. The "Hunnish"engine cowling and the rearward position of the pilot's seat com- bined to make the D.H.9 look quite different from the D.H.4,despite its close relationship to the earlier type. The construction of the fuselage was reminiscent of the DHA.It was a wooden structure, with wire cross-bracing abaft the observer's cockpit; the forward portion embodied several woodendiagonal members and was plywood-covered. The lower longi- tudinals embodied sturdy patons which extended rearwards fromthe forward undercarriage legs to the rear of the observer's cock- pit. Extensive use was made of plywood for formers, and therearmost bay of the fuselage was plywood-covered. The under- carriage had two substantial wooden vee struts, to the apices ofwhich the axle was bound by rubber cord. The steel-shod wooden tail-skid was also> sprung by rubber cord. As on the D.H.4, theobserver's cockpit contained a dual set of flight controls, but engine controls were not duplicated. The main petrol tank was divided longitudinally into twoseparate compartments, each of which was fitted with a windmill- driven pump. Provision was made for the two compartments ofthe tank to be interconnected in the event of failure of one of the pumps. Fuel was pumped up to the 8-gallon gravity tank in thecentre-section, whence the engine was fed. The main tank was clothed in a loose coyer of doped fabric which was intended todrain petrol away rapidly if the tanks were hit. From his position behind the wings the pilot had a good viewin most directions. In an attempt to improve his downward view a cut-out was made in the root of the starboard lower wing. Withits pilot and observer close together, the D.H.9 ought to have been a better combat aircraft than the D.H.4, but the improved seatingarrangement did not compensate for the lack of the performance necessary to evade the German fighters. The D.H.9 was placed in production on a large scale withseveral contractors. Deliveries did not begin until the end of 1917, but production gained momentum rapidly until output wasat the rate of one complete aircraft every 40 minutes. Peak pro- duction was reached in the middle of 1918: during the quarterwhich ended on June 30th, 1,156 D.H.9s passed inspection, and during the next three months the total was 1,052. During thefinal quarter of the year, 660 were passed. Although the D.H.9 will always be associated with the Indepen-dent Force, it had its baptism of fire in the hands of Squadrons Nos. 98, 206 and 211. All three of these units were in Franceby April 3rd, 1918; Nos. 98 and 206 were with the II Brigade, while No. 211 was allocated to the VII Brigade. As the threeD.H.9 squadrons were arriving in France, enemy activity began to increase in the La Bassee area, and by April 6th it was evidentthat preparations for an offensive north of Aubers were well advanced. Any doubts about the enemy's intentions weredispelled by a heavy bombardment with mustard-gas shells on the night of April 7th/8thj and on April 9th the German Sixth Armyattacked along a line between Armentieres and the La Bassee canal. The Battle of the Lys had begun. The D.H.9s of No. 206 Sqn. had already been in action. OnApril 2nd they had twice raided Don railway station, and on the 7th had dropped five 112-lb and eighty-seven 25-lb bombs onHaubourdin station. By April 11th, the Battle of the Lys was raging fiercely, and Nos. 98 and 206 Sqns. bombed Wervicqand Armentieres. On the following day Sir Douglas Haig issued his famous "backs to the wall" order; during that day nineteenpilots of No. 206 Sqn. flew a total of 76 hours. The morning found them, in company with No. 98, attacking German lines ofcommunication at Comines, Quesnoy, Frelinghien and Haubour- din; and in the afternoon of that critical day both units werediverted to the Merville area. The D.H.9s of No. 98 Sqn. dropped a total of fifty-five 112-lb bombs from 2,500ft on enemytroops and transport at Neuf Berquin, Estaires and Steenwerck. At 6.30 p.m. No. 206 Sqn. dropped twenty-one 112-lb bombs ontargets between Armentieres and Estaires. Bad weather hampered bombing activity during much of the remainder of the battle,which ended on April 29th. Despite the good work it did as a tactical bomber, the D.H.9is best remembered for its service with the Independent Force and for the strategic bombing it performed with the squadronsof that Force. As the Battle of the Lys was ending, most of the D.H.9s and crews of No. 99 Sqn were at St. Omer, awaitingsuitable weather for their flight to their aerodrome at Tanton- ville, south of Nancy. The opportunity came on May 3rd, butthe 240-mile flight was too much for the engines of the aircraft, which provided a foretaste of the troubles which lay ahead—broken valve springs and minor defects were found on nearly every engine. Soon after their arrival at Tantonville, the pilots of No. 99Sqn. discovered the D.H.9's woeful lack of operational perform- ance. The squadron history records: — • ~ '"It was found that single machines could seldom climb above 16,000 feet in 75 minutes without bombs, or 14,000 feet in the same time withone 230-lb or two 112-lb bombs. Most engines ran very badly, and used far too much petrol above 10,000 feet, owing to the defective altitudecontrol on the Zenith carburettor. This was afterwards enormously improved by a Squadron modification, and the average petrol consump-tion reduced from about 15 gallons an hour to less than 13." That history contains many references to engine trouble; therepeated defections of the Pumas constitute a kind of continuous accompaniment over which themes of determination and gallantryare woven simply, starkly or magnificently: — "The 29th (of May) was a thoroughly unlucky day. Fourteenmachines of 'A' and 'C Flights started for Thionville, 32 miles over the lines. Finally, only six machines completed the raid. Of the eight whichfailed to cross the Lines, one machine broke a petrol pipe, another had a broken oil pipe, and a third a badly missing engine; the remainder wereunable to keep up at a height owing principally to defective vacuum control and broken valve stems." A later entry reads: — "Eventually only six machines performed the raid [on Metz, June 1st, 1918] out of the thirteen which started. The majority of the machines which did not cross the Lines were unable to keep pace at a height, and it was agreed, after talking the matter over, that leaders should attempt rather to take full formation over the Lines than to climb an extra 500 feet, which would in any case be insufficient to enable the D.H.9s to avoid the German scouts .... At this time the Squadron was passing through a period of depression. One or more valve springs had broken on at least three out of four engines which went up on a raid, and this, com- bined with frequent carburettor and petrol pipe troubles, made it most difficult for the fitters to keep the engines serviceable .... The pilots and observers were also much downcast by the frequent failure of the machines even to reach 13,000 feet in a reasonable time when carrying bombs .... An expert from the Siddeley Company was attached for about ten days at this time, who helped considerably, but was unable to discover anything in connection with the maintenance of engines beyond what was already known to Chief Master Mechanic Martin. The first case of a cracked cylinder head was now found on an engine, and thest became more frequent as the weather became warmer."The bogy of engine trouble recurs time after time: — "On June 4th . . . the two emergency machines returned after seeingtwelve machines across the Lines, but unfortunately two others were compelled to return shortly afterwards, Lt. Beecroft with a broken oilpipe, and Lt. Marshall with a cracked cylinder head." "Engine trouble again defeated the Squadron on the 6th, only elevenmachines of 'A' and 'B' Flights actually getting into the air, of which six finally returned without crossing the Lines.""The next day's work was even more depressing, as only four machines reached Thionvtlle, under Capt. Purser, out of the twelve which startedfrom 'B' and *C Flights. Several machines . . returned with various cngine$ troubles. . . ," (Continued on page 392)
Sign up to
Flight Digital Magazine
Flight Print Magazine
Airline Business Magazine
E-newsletters
RSS
Events
