Introduction.

                   The above aeroplane is the first of the type fitted with two 20 m.m. cannon guns and electrically heated Mark VIII pitot static head. In other respects the aeroplane was similar to Spitfire K-9793 reported on in the First Part of Report M/692,b dated the 12th July 1939.

                   The cannon gun installation, one gun in each wing, was very neat and except for two slight bulges on the upper and lower surfaces of the wing at the rear spar, the standard wing section was maintained.

                   The aeroplane is fitted with a 2-pitch 3 blade metal airscrew and it was desired to compare the handling and the performance of the aeroplane with that of Spitfire K-9793, fitted with Browning guns and 2-pitch metal airscrew.

Summary of Results.

(1)              The position error of the electrially heated Mark VIII pressure head which was situated in the same position as the Mark VA head on previous Spitfire aircraft, is the same at high speeds and practically the same at low speeds.

(2)              The handling of the aeroplane in normal flight, at the stall, in aerobatics and in dives, is unaltered by the cannon gun installation.

(3)              The effect on the handling of short bursts from the cannon guns was detected but was negligible.

(4)              The top level speed is about 3 m.p.h. less than the Spitfire fitted with Browning gun installation.

                   The following Table shows the comparison in speed and climb for the Spitfire fitted with 2-blade wooden airscrew and Spitfires fitted with 2-pitch 3-blade metal airscrews and differing only in their guns installations.

Aeroplane:-K-9787K-9793L-1007
Engine:-Merlin IIMerlin IIMerlin III
Airscrew:-2-blade Wood
3001700
D.H. Type
N.P3-5-5-7*
D.H. Type 5/21*
Time to 20,000 ft.9.4 mins.11.4 mins.10.7 mins.
Speed at 18,500 ft.363 m.p.h.367 m.p.h.364 m.p.h.
Service ceiling31,900 ft.34,400 ft.34,500 ft.
Log book H.P. for
2600 r.p.m. at 12250 ft.
966998953
 
*The same pitch setting were used for K-9793 and L-1007.


SUMMARY OF TRIALS

AEROPLANESpitfireNo. L-1007
SPEC. NO.-
CONTRACT.48291
CONTRACTORVickers-Armstrong Ltd.

TYPELandplaneDUTY    Fighter.
 
ENGINES.Merlin IIINormal B.H.P    953     at Rated Altitude 12,250 ft
 
At     2,600     R.P.M.    

 lb.
Tare weight4599
Weight light 
Fixed military load 
Service Load  647
Fuel         gallons*  630
Oil        49
Flying weight on trials.5925

* Based on 7.5 lb. per gallon.

At Full Throttle
Height
Feet
Top
Speed
M.P.H.
Time
To
Climb
Mins.
Rate
of
Climb
Ft./Min.
    S.L. --
    2,000 1.01970
    5,000 2.52040
  10,000 4.92170
  15,0003487.51750
  20,00036210.7  1320
  26,00035416.4    820
  18,600364   

Service Ceiling34,500 ft.Landing speed     M.P.H./Kts.
Take off run  yds.   Time   secs.Distance from rest to clear     ft. screen      yards
Stalling speed             M.P.H./Kts.Gliding in A.S.I.     M.P.H./Kts.
Best landing A.S.I.         M.P.H./Kts.Distance to rest (with brakes after clearing 50 ft. screen yds =    
 
Landing and take off tests corrected to  


CLIMBING TRIALS

Height in
Standard
Atmosphere
Feet
Time
From
Start
Min.
Rate
of
Climb
Ft./Min.
True
Air
Speed
M.P.H.
A.S.I.
M.P.H.
P.E.C.Comp.R.P.M.Boost
lb.sq.in.
Sea Level0       
  1,0000.5          
  2,0001.01970188   187   -4.5-2170+6.4
  3,0001.51990191   187   -4.5-2220+6.4
  5,0002.52040196.5187   -4.4-0.32265+6.4
  6,5003.22080201   187   -4.4-0.42310+6.4
  10,000*4.92170211.5187   -4.4-0.72420+6.4
13,0006.41920220   185   -4.1-0.92420+4.1
15,0007.51750222.5181   -3.5-1.02420+2.7
16,5008.41620225   178   -3.1-1.02415+1.7
18,0009.31490227   175   -2.6-1.12410+0.8
20,00010.7  1320230   171   -2.0-1.22405-0.4
23,00013.2  1070234.5165   -1.1-1.42395-2.0
26,00016.4    820238.5158.50-1.52395-3.5
28,000          
30,000            

Estimated absolute ceiling         35,800Greatest height reached      25,600
R.P.M. stationary on ground     2500Boost pressure lb./sq.in.    +6½
* Full throttle height
** Service ceiling   (estimated) 34,500 ft.


SPEED TRIALS

Height in
Standard
Atmosphere
Feet
True
Air
Speed
M.P.H.
A.S.I.
M.P.H.
Compressibility and
Position
Error
Correction
M.P.H.
R.P.M.Boost
lb/sq.in.
Speed at
Normal
Revs.
P.E.C.Comp.
Sea Level        
  1,000        
  2,000        
  3,000        
  5,000        
  6,500        
10,000        
13,000339   289.5-8.5-3.22860+6.3 
15,000348   288   -8.5-3.52925+6.3 
16,500354.5286.5-8.5-3.92975+6.3 
18,000360.5285   -8.5-4.33020+6.3 
20,000362.5277.5-8.5-4.73035+5.1 
23,000359   262   -8.5-5.02995+2.6 
26,000354   246   -8.0-5.02940+0.2 
28,000        
30,000        
  18,600*364   285   -8.5-4.33045+6.3 

Landing and take off tests corrected to    
Take off run               yds.     Time     Secs
Distance from rest to clear               foot screen           yds.
Gliding in A.S.I.             M.P.H.Stalling speed           M.P.H.
Best landing A.S.I.             M.P.H.
Distance to rest (with brakes) after passing over 50 ft. screen             yds.
Landing run with brakes             yds.Landing run without brakes         yds.

*Full throttle height


Handling
1. Weight and centre of gravity position

Spitfire K-9793
Browning guns.
Spitfire L-1007
Cannon guns.
Weight light   4599 lb.   4599 lb.
Guns.200218
Ammunition.150106
Instruments, etc.107123
Pilot.200200
Fuel.630630
Oil.  49  49
____________________
Total weight   5936 lb.   5925 lb.

Handling trials were made at the following centre of gravity position:-
1. Normal C.G. position 7.5 ins. aft of the datumThe same as
for K-9793.
2. Extended aft C.G. position 8.4 ins. aft of the datum
by the same pilots who tested Spitfire K-9793. 

Handling Characteristics

                   In normal flight, at the stall, and in aerobatics, the handling of the aeroplane was the same as Spitfire K-9793 (see First Part of Report M/692,b. dated 12th July, 1939) at both of the above centre of gravity positions.

                   Handling in the dive which was only checked at the extended aft position of the centre of gravity, was also the same as for Spitfire K-9793.


Inspection and Test Certificate.

[WWII Aircraft Performance] [Spitfire Mk I]