The Development of Combat aircraft

[Ed Rotondaro]

Hi:

As part of the thread on battleships and bombs, the discussion was turning to the advances in aircraft during the 1920s and 1930s that really made them a dominate weapon. I was curious as to why the pusher propeller planes were so prevalent early in WWI. Was it an easier design to build and fly? Did it turn out to be more vulnerable to combat damage since it's engine was rear mounted? Was it better suited for recon with pilot and observer? Any thoughts?

[old_pop2000]

Hi:

As part of the thread on battleships and bombs, the discussion was turning to the advances in aircraft during the 1920s and 1930s that really made them a dominate weapon. I was curious as to why the pusher propeller planes were so prevalent early in WWI. Was it an easier design to build and fly? Did it turn out to be more vulnerable to combat damage since it's engine was rear mounted? Was it better suited for recon with pilot and observer? Any thoughts?

There are a couple of advantages of the pusher over the tractor type. First, aerodynamically the propellor is placed closer to the elevator and rudder increasing the airflow over those controls, improving low speed handling. Second, is of course visibility for recon. Third, wing effeciency is improved by removing one source of turbulent air on the wing, which decreases lift and increases form drag.

There some disadvantages like FOD damage to the props, from the landing gears. Danger to the pilots during bailout. In tractors, the propellor can supply needed cooling air to the engines that a pusher does not. Flap area is reduced as it is difficult to install flap systems on pusher and they are less effective without the air from the prop. Excess noise from exhaust flowing through the prop.

One WWI use was the lack of a satisfactory interruptor gear for the Allies that was remedied by using the pusher and placing the pilot in the nacelle in the front. DeHavilland used this configuration but it was not long lived.

The configuration is still used. The B-36 used a pusher style configuration as did the Cessna 337 Super Skymaster and the O-2A/B Push n Pull light observation aircraft used by FAC's in Nam. The plane's nickname was the "oscar deuce".

[Ed Rotondaro]

There are a couple of advantages of the pusher over the tractor type. First, aerodynamically the propellor is placed closer to the elevator and rudder increasing the airflow over those controls, improving low speed handling. Second, is of course visibility for recon. Third, wing effeciency is improved by removing one source of turbulent air on the wing, which decreases lift and increases form drag.

There some disadvantages like FOD damage to the props, from the landing gears. Danger to the pilots during bailout. In tractors, the propellor can supply needed cooling air to the engines that a pusher does not. Flap area is reduced as it is difficult to install flap systems on pusher and they are less effective without the air from the prop. Excess noise from exhaust flowing through the prop.

One WWI use was the lack of a satisfactory interruptor gear for the Allies that was remedied by using the pusher and placing the pilot in the nacelle in the front. DeHavilland used this configuration but it was not long lived.

The configuration is still used. The B-36 used a pusher style configuration as did the Cessna 337 Super Skymaster and the O-2A/B Push n Pull light observation aircraft used by FAC's in Nam. The plane's nickname was the "oscar deuce".

Dennis:

Interesting that tractor versus pusher each had strengths and weaknesses. Since we see so many tractor type planes I had mistakenly assumed it was vastly superior. The Germans fielded a psuh pull fighter during WWII in small numbers that was built by Dornier. The Do-335 Pfiel (Arrow) had a top speed of 474 mph. Good thing they only built 38 of them.

[old_pop2000]

As most of you should be aware, radial engines have some distinct advantages and disadvantages over inline engines. One disadvantage was the disruption of the flow of air as it passed over the cylinder heads. One of the most important contributions to aviation took place in 1929 when the N.A.C.A. released test results of placing a sheet metal ring around a radial, terming it the N.A.C.A. cowling. The results showed the drag caused by the radial cylinders was reduced by one-fifth and cooling was not affected. To improve and maintain airflow, baffles were used inside the ring of sheet metal. This improvement greatly increased the flow of air and hence the cooling of the engine. It wasn't until six years later, 1935 that detailed comprehensive testing was able to quantify the data and present some better methods and improvements.

Tests broke down the cowling into two parts: the nose section and the exit slot. Each part serves a different purpose. The nose section cleanly separates the airflow into the part moving outside the cowling from that which enters the cowling cooling the engine. The exit slot's purpose is the smoothly recombine the air exiting the baffle with the air moving over the cowling. The exit design controls the amount of air cooling the engine. Cowling flaps are a function for the control of the amount of air cooling the engine. These are open during taxing and take-off and landings.

This invention made possible the improved performance of radial engines in regards to power, because power generates heat which is the achilles heel of all high powered piston engines.

[john964]

There are a couple of advantages of the pusher over the tractor type. First, aerodynamically the propellor is placed closer to the elevator and rudder increasing the airflow over those controls, improving low speed handling. Second, is of course visibility for recon. Third, wing effeciency is improved by removing one source of turbulent air on the wing, which decreases lift and increases form drag.

There some disadvantages like FOD damage to the props, from the landing gears. Danger to the pilots during bailout. In tractors, the propellor can supply needed cooling air to the engines that a pusher does not. Flap area is reduced as it is difficult to install flap systems on pusher and they are less effective without the air from the prop. Excess noise from exhaust flowing through the prop.

One WWI use was the lack of a satisfactory interruptor gear for the Allies that was remedied by using the pusher and placing the pilot in the nacelle in the front. DeHavilland used this configuration but it was not long lived.

The configuration is still used. The B-36 used a pusher style configuration as did the Cessna 337 Super Skymaster and the O-2A/B Push n Pull light observation aircraft used by FAC's in Nam. The plane's nickname was the "oscar deuce". You forgot the X/YB-35

[old_pop2000]

You forgot the X/YB-35

Actually, I left off a few, but space did not permit all of them. YB-35 was, in fact, a pusher type bomber.