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F540 Operations Record Book November 1940 for 420 Flight Middle Wallop.
PRO Kew No. AIR27 Piece 751 Microfilm Row1 Draws 52-71
Place Date Time Summary of Events References to Appendices
Middle Wallop 2/11/40   Harrow K. 6993 collected from Farnborough. Found to be u/s & returned.  
" 6/11/40   Mentor L. 4404 collected from No 6 OTU Button Bridge.  
" 8/11/40   Battle R. 7472 collected from No 9 MU. commenced fitting L.F.F.  
" 11/11/40   Flt. Lt. P.L. Burke visited Vickers Works, Dartford and inspected drawings
of racks and release mechanisms designed for DB 7.
" 12/11/40   Flt. Lt. P.L. Burke flew to Farnborough and collected plywood bulkheads
for fitting between bomb compartments of Harrow K. 7020.
" 13/11/40   Racks on Harrow K. 7020 cocked and fired and found correct.
Plywood bulkheads fitted and aircraft flown to Farnborough for
loading with dummy mines.
" 14/11/40   Test drop with dummies carried out over sea south of Worth Matravers
Cinimatographic record taken from escorting Battle.   15 mines "hung
up".   Aircraft flown to Farnborough for investigation.
" 16/11/40   Flt. Lt. P.L. Burke flew to Farnborough to see film of test drop
carried out on 14/11/40.
" 17/11/40   Harrow K. 7020 returned from Farnborough with racks again serviceable
and loaded with dummies.
" 18/11/40   Drop test with dummy mines carried out.   Harrow escorted by Blenheim
and photographic aircraft.   Level curtain laid, but 48 mines "hung
" 19/11/40   Harrow K. 7020 returned to Farnborough.   Discovered that a slack
bearing in one of the distributors was jamming, preventing some
of the racks from receiving impulses.
Middle Wallop 20/11/40   Visit from Group Captain Rowley from Air Ministry  
Middle Wallop 21/11/40   F/Lt Burke and Group Captain Rowley watched release trials of "Aircraft
Patents" rack designed for the DB 7.   Release rapid and fairly even
and all dummies released.
Farnborough 21/11/40   F/Lt D Hayley-Bell took Harrow K. 7020 to 16000 feet with empty
racks which were all cocked and fired release to test freezing
conditions at this height.   Test successful.
Middle Wallop 22/11/40   Live drop test carried out.   Details are contained in attached report APPENDIX "A"
" 23/11/40 AM. Air Marshal Sir Philip Joubert paid a visit to the Flight.
Wg Commander Homer and F/Lt. Burke visited HQ. Fighter Command
to discuss establishment of proposed DB 7 Squadron.
Middle Wallop 25/11/40   F/Lt. Hayley-Bell and P/O Hoy visited Sector Operations Room to
study the organisation and learnt sector code place names.
" 27/11/40 PM. Drop test carried out with modified mines from Harrow K. 6993.
Pilot:- F/Lt. Burke.   Passengers:- S/Ldr Traill of No 10 Group and
Mr Owen of RAE Farnborough.   Escorted by Harrow K. 7005 for
observation.   Pilot:-   W/C. Homer.   Passengers:- Mr. Lockspeiser of
M. AP.   Mr. Pritchard of R.A.E. and W/C Osbert.   Two mines
exploded prematurely and damaged aircraft slightly, which
was however, landed safely at Middle Wallop.
" 28/11/40   The following assembled to discuss possible reasons for the accident
on the previous day:- Mr. Lockspeiser, S/Ldr Garner, Mr. Whittaker
R.A.E. Prof Hill and Mr. Hind of AM RL Exeter, W/C Mack??
of Air Ministry and F/Lt. Burke.

Form 541 No 420 Flight

From 00.01 hrs 1/11/40 to 23.59 hrs 30/11/40

Aircraft Type and No. Crew. Duty. Time Up. Time Down. Details of Sortie or Flight References.
No. 420 Flight. Middle Wallop.                                                      APPENDIX "A" to Form 540.

RESULTS OF TRIALS OF AAD. TYPE A. - MIDDLE WALLOP - 22/11/40.                                        10     

       Five hundred modified bombs arrived on the station from Chorley at
about 22.00 hours on 21/11/40.   These bombs were not fitted with
detonators, and it was not possible to unpack, fuze, and exchange bombs
in time to use a load of these bombs in time for the trial the following
      Previous to this the armourers of 420 Flight had modified half a
load (80 bombs) by firing the Bickford fuze initiating cap.   It was
decided to carry out a trial with a load consisting of these 80 bombs,
together with 80 unmodified bombs.   The reasons for taking this decision
          (1)  The extreme urgency of the trial.   It should be noted that
                it was quite impossible to carry out the trial on the 22nd
                with a full load of modified bombs owing to lack of time.
          (2)  The weather was excellent and all the necessary arrangements
                for the trial had been made.
          (3)  The containers had been so modified that the lids could not
                come off until they were clear of the aircraft.
          (4)  Tests have shown that "flash back" causing premature
                detonation only ocurred in about 1 per cent of bombs.
      After consultation between G/C Rowley, F/Lt. Burke and D.Arm D's
representative, it was decided to accept the slight risk of premature
detonation (which could not occur, as previously, with the bomb in contact
with aeroplane) in hope of being able to clear the apparatus for
operational use on the night of the 22nd in accordance with the Secretary
of State's expressed wishes for getting into action against the enemy at
the earliest possible date.
      On the morning of the 22nd a full test was carried out of the
electrical release gear, after which the work of loading the 160 mines on
to the carriers was started.   This is a long job and the men had had no
previous experience in fitting the containers to the modified carriers.
      The aircraft, complete with photographic aeroplane, another Harrow
carrying observers, and escorting Spitfires set out at about 14.15 hours,
but had to return owing to enemy being reported in the vicinity.
      The aircraft set off again at about 16.30 without the photographic
aircraft as the light was now too bad.   The curtain was laid at about
17.00 hours from about 5,000 feet.   Results were:-
          (1)  The mines left the aircraft as they should, regularly, evenly
                and forming a very impressive looking curtain.
          (2)  After a certain number had been released, there was a premature
                which appeared to take place some distance behind the laying
                aircraft.   This was followed by a second, rather closer, and
                a third which looked to be some distance away.   There was a
                considerable number of mines between each premature.
          (3)  Although the curtain as a whole was regular fifteen parachutes
                were considerably above the level of the remainder and two
                below.   Of the high ones, three were probably due to the
                weak link resulting from the necessary use of a double breaking
                link.   This is a modification necessitated by errors in manu-
                facture.   The two low ones were due to delayed opening of their
          (4)  On returning to the aerodrome the pilot of the laying aircraft
                reported feeling his tail lifted by the prematures and that
                after the third of them he switched off the laying gear.   An
                observer in the laying aircraft said that he noticed a small
                tear in the fabric.   The slipstream got into this tear, and
                on the way home, removed much of the fabric from one side of
                the aircraft.   From a superficial examination it does not
                appear that any damage has been caused to the structure of the
          (5)  One mine on the bottom layer was found to have hung up in a
                similar way to that which caused the accident on 26/10, but on
                this occasion the modification to the rack and aircraft were
                effective and the pin was not withdrawn from the lid of the
                container.   The apparatus therefore remained in a safe con-

- (2) -


          (1)  With unmodified mines flashback may result in a definite danger
                of prematures,

          (2)  The modifications to carrier and aircraft do ensure that there
                is no danger from "hang ups",

          (3)  Although these modifications do ensure that the mine is clear
                of the aircraft before the lid is free to come off, the blast
                effect from a premature may still cause damage to a metal.
                covered aeroplane although such damage is not likely to be
                serious and should be negligible on a fabric covered aeroplane,

          (4)  It is recommended that a further trial should be carried out as
                as soon as possible with modified mines.

                                                (Signed)   H. Rowley.   G/Capt.

                                                (Signed)   J. W. Homer.W/Cdr.

                                                 (Signed)   P. L. Burke, F/Lt.

                                                (Signed)   W. Rathbone, F/Lt.


             1.    To get Harrow K. 7020 repaired by R.A.E.
             2.    To collect Harrow K. 6993 modified for operational use
                    from R.A.E. on Monday 25/11/40.
             3.    To carry out a further "live" drop on Tuesday 26/11/40.
             4.    If trial successful, operate on Tuesday night.