August 24, 1016 
LAND & WATER 
T5 
Pouncing on a slower machine helow — Tlie fixed gun in A's aero- 
plane is aimed alonij the path of flight at the lower machine, whose 
Gunner B is unable to fire at A because he is blanksted by his 
own planes 
who were laden >vith bombs, or who with slower double- 
seater machines were engaged on the painfully trying 
work of directing our artillery tire or photographing the 
new trenches, or the latest movements of troops. War is 
war, we have done just the same to them, with at Ic^ast 
equal success and with less advertisement. In the earlier 
stages of operations, when the (iermans had no machines 
of the type, we were operating with engines of 80 H.P., 
■"such as the Gnome, and shortly after with engines of 
QO H.P.., such as the Le Rhone. 
I now come to the sub-division which exists amongst 
these little aeroplanes — between "tractors" and 
" pushers " — those which have the engine and propeller 
in front and those which have them behind the pilot, as 
shown in diagram No. 2. • 
This subdivision is important, because it shows how 
various advantages may be got by special means. 
The " tractor," owing to the smooth fish shape which 
can be given to its body, shown shaded in the chagram, 
and the small number of projecting struts and wires to 
offer resistance to the air is, with the same engine power, 
always capable of more speed and a quicker climb than 
the '' pusher." There is .as yet no exception to this rule. 
In view of the principle previously declared on which 
these little craft are built, of sacrificing everything to 
mobility, it is a wonder that the " pusher " was ever 
allowed to appear amongst the typo. There are certain 
authorities who think that it never should have been 
allotted to these duties, but others arc of opinion that 
certain peculiar ad\antages of the " pusher " warrant 
the loss of speed. 
Advantages of the Pusher (see diagram 2) 
The advantages are the splendid field of fire and field 
of view forward which is given by this arrangement, 
advantages which not only make it easier for the airman 
to aim at the enemy when not in the direct line of flight, 
but make it easier for him to find his enemy when mount- 
ing into the upper air after him. 
It is to be noted that I said it was easier to aim the 
gun at an enemy who may be moving across the path 
of flight, not that it was easier to hit him, and this is the 
crux of the question. 
A target moving across the field at qo miles an hour 
is extraordinarily difficult to hit. There is so iittle time 
to use the sights, to allow for the cross speed, to allow 
for one's own speed, to allow for the great and disturbing 
influence of the wind pressure when once it gets on 'to 
the side of the gun. To the enthusiast for the tractor. 
it is an accepted fact that one never — or so rarely as not 
to count, hits an enemy mortally, except when he is 
moving in a direct line away or towards, and hence that 
the freedom of aiming sideways loses all its attractions. 
Thereby' we are left in the same suspense as before 
as to whether little " pusher " machines, are, with the 
average skilled pilot, as useful for defence as the "tractors." 
To fix our ideas on the speeds without pretending to 
precision, we must take it that these fast single seater 
tractors at the beginning of the war had a speed which 
we may call 75 miles an hour at 6,000 feet ; those which 
t ame later had a speed of 86 miles an hour and the 
fast pu-shers a speed of 83 miles an hour at the same 
heights.* 
I do not propose to allow myself to be entangled in 
the sea of rubbish which has been tlowing and ebbing 
over the difference between privately flesigned machines 
and those (distinguished by the letter " E ") which were 
(iovernment designed. I have enquired carefully into 
the question and find that there is nothing whatever in it. 
There are excellent machines from b(jth sources, and 
owing to the rapid strides which e\eryonc has made, 
whichever machine has been designed latest is generally 
the best in some particular feature which has had con- 
centrated study. 
The Radial Engine 
The effect of the kindof engine used in these aeroplanes 
must be considered. Where supremely light weight is 
wanted in the finished aeroplane it is proper to pick out the 
engine of least weight for power ; that is to say the engine 
which together with its fuel, oil, tanks (and supports, 
accessories, and silencers if any) is lightest for the num- 
ber of hours of flight contemplated- for the type, 'fhis 
means that the " single seater short range " defender 
aeroplane should always have a radial engine ; because 
up to the present date the radial engine is under these 
conditions of use lighter than any and every type of 
non-radial engine. 
To bring this fact home I have drawn diagram 3 — 
where it is shown that by disposing the cylinders starwise 
round the crank we get a crank case which is exceedingly 
small, light, and stiff : wliich carries the minimum 
number of bearings and generally saves weight. If the 
question is then asked why in aeronautics any other engine 
than a radial one is ever used, I must ask to be allowed 
to defer the answer till I can deal with the engine ques- 
tion at greater length. 
For the same reason of \\eight-sa\ing and maxini'im 
power the single seat " defender " does not carry silencers, 
and therefore may appropriately use the class of engine 
which is not easily susceptible of being silenced, the rotary 
radial. * 
The Risks 
Having now given some idea of the class of aeroplane 
which is atxjve all mobile, I accentuate that it does not 
normally travel much over the enemy's country, and is 
• Throughout these notes the figures of numbers, speeds, etc., arc 
krpt sutliciently comparative for instruction, but they are carefully 
disguised, so as to avoid by any possible chance disclosing information. 
Single seater 
'Tushei^' 
Single seater 
"Xr3.ctov" 
Diagram 2 showing the superior freedom for moving the gun to fire 
in all directions except backwards in a "pnsher" as compared to u 
" tractor " single seater. It is a question whether the extra 5 or 8 
miles an hour of the " tractor" compensate for the loss of field of fir« 
