Although we think of air-to-air radar as a relatively modern invention, it first made its appearance in WWII. Some late war fighters featured the AN/APS-13 Tail Warning Radar to alert the pilot when an enemy fighter was on his tail. In [WWII US Bombers]’ fascinating video we get a deep dive into this fascinating piece of tech that likely saved many allied pilots’ lives.
Fitted to aircraft like the P-51 Mustang and P-47 Thunderbolt, the AN/APS-13 warns the pilot with a light or bell if the aircraft comes within 800 yards from his rear. The system consisted of a 3-element Yagi antenna on the vertical stabilizer, a 410 Mhz transceiver in the fuselage, and a simple control panel with a warning light and bell in the cockpit.
In a dogfight, this allows the pilot to focus on what’s in front of him, as well as helping him determine if he has gotten rid of a pursuer. Since it could not identify the source of the reflection, it would also trigger on friendly aircraft, jettisoned wing tanks, passing flak, and the ground. This last part ended up being useful for safely descending through low-altitude clouds.
This little side effect turned out to have very significant consequences. The nuclear bombs used on Hiroshima and Nagasaki each carried four radar altimeters derived from the AN/APS-13 system.
Very cool!
The idea of a bell ring is so darling.
How did the radar work? Did it time returned pulses or some sort of interference effect with varying frequency? Video didn’t seem to cover it and I don’t know how radar worked back then at all!
If they already has a functioning radar back then, why didn’t they integrate it with minigun to create CIWS like AK-630? They could’ve saved countless lives of air crews.
They did…. in the B-29
this is far different from that. sounds like just a tx with a fixed oscillator, a fixed directional antenna, and an rx with some sort of time-of-flight probably based on an interferometer or — for all i know — a passive rc filter. comparable capabilities to the ultrasonic or infrared sensors in airport bathroom sinks. but it’s obviously a step on the path to more complex radar
It might not even have had a time of flight. It may have been any reflection at all that exceeded the receiver’s detection threshold, and relied on volume dissipation to not false trigger off something 2 km back.
Probably because the computer necessary to compute real time targeting solutions for said gun were prohibitively expensive, heavy, and too limited to be practical in 1942.
Gunlaying radar was a real thing. They attached it to a bunch of Bofors autocannons and it came late in the war, but it was made. See https://en.wikipedia.org/wiki/Radar,_Anti-Aircraft_No._3_Mk._7
WAAAAY too heavy for a fighter. They put stuff like this in bombers, but fighter pilots cared so much about weight that they’d have armorers remove the outermost pair of wing guns to enable them to roll faster in dogfights.
Early radar was also surprisingly bulky!
Lancaster bombers had rear warning radars as well called Monica, but they were turned off, when it was found that German night fighters were using the emissions to track them
https://en.wikipedia.org/wiki/Monica_(radar)
Apologies, just reliased AN/APS-13 and Monica were basically the same radar. AN/APS-13 was just the US designation of the British Radar. I guess there were more benefits for a fighter since they are unlikely to be targeted
The British, (who developed this tail warning system as monica) did.
Some Lancaster bombers were fitted with the ‘Village Inn’ automated radar rear gun laing system. Which was installed and used on night raids. However it still depends on the gunner preventing friendly fire incidents as almost all the aircraft detected would be friendly.
As the effectiveness of Mosquito night fighters being used as intruders overwhelmed the german night fighter defences, the Village Inn system was removed from use.
Various Infra Red Night Vision and identification systems had been added to the Village Inn system ‘tabby’ ‘f equipment’ and ‘z equipment’, but it was still best to leave the hunting to the dedicated night fighters who could spend time identifying their prey.
this was supposed to bea reply to ‘Vauxhall Astra’ ‘s comment.
Funny that you can buy tail radar systems these days on sellers like Aliexpress, albeit for bicycles ;)
That will come in handy for the cannons in the integrated rear-facing turret.
If you stay on the cycle lane you might not need it.
If you’re happy enough to live in a country that has cycle lanes in the first place.
A little over a decade ago Corvette Racing started using it in GT racing like Le Mans. It was done as graphics on the rear view display, showing left/right and approach speed of cars behind
The Germans plugged to into the purpose of the Monica ARI 5664 (US AN/APS-13) tail warning set sampled from crashed bombers, and developed the FuG 227 Flensburg receiver, which allowed night fighters to home in on the Monica signals from up to 100 km. Luckily for RAF Bomber Command, a German night fighter equipped with Flensburg accidentally landed at an RAF base a few months after its deployment, and word went out to turn off Monica.
It was already well being phased out by then, as an earlier increase in losses to nightfighters had been spotted, and it was theorised that such a system existed.
A replacement was then quickly created, ‘fishpond’ which was a simple additional crt display added to the existing H2S navigation radar. This sytem produced a picture of aircraft approaching/below the bomber. Since it was much more effective than Monica it was being rapidly installed when the Flensburg system was identified, and the remaining monica sets were simply turned off.
Fishpond was much harder to detect since it used the microwave bands.
Volume 2 of the Surplus Radio Conversion manual described how to convert it to a 420 MHz HAM band transmitter & receiver