Somebody actually did do this, and imagine our lack of surprise that it was the Germans in World War II, those same whacky guys who never let mere impracticality stand in the way of weapons development. These are the same guys who came up with explosive robot tanks that were tethered to the human operator by a short and vulnerable control wire, and a sound-pressure weapon that could shatter enemy troops and aircraft with sound waves (technical problem: it was also fatal to any human operators, which turned out to be an unavoidable impediment to combat deployment). So why not a flamethrower on an airplane?
Hell, why not two?
The German aero-military historical page, LuftArchiv.de, has a short blurb on this with two photos of one of the weapons (it’s at the end of the page that has some other interesting weapons, including a quasi-automatic 88mm recoilless rifle with a ten-shot drum magazine and a 10 rounds per minute rate of fire). Here’s their explanation:
Bereits Ende 1939 machte Leutnant Stahl, Technischer Offizier beim KG 51, den Vorschlag, angreifende Jäger durch im Heck der Bomber und Fernaufklärer eingebaute Flammenwerfer abzuwehren. Der angreifende Jäger sollte in die ausgestoßene Ruß-Ölwolke hineinstoßen, so dass seine Kabinenscheiben schlagartig blind wurden. Im Februar 1940 fanden entsprechende Versuche mit He 111 und Ju 88 in der Erprobungsstelle Tarnewitz statt. Das Gerät wurde dann auch probeweise bei Beginn des Russlandfeldzugs beim KG 51 eingesetzt, scheint sich aber bei der Truppe nicht durchgesetzt zu haben. Als Angriffswaffe wurden die Flammenwerfer »Gero 11« A, Bund C bei der Fw 190 für Tiefangriffe verwendet.
What’s that? You don’t read German? How does it feel to be dumber than a third-grade kid… in the German-speaking countries? Here it is in quick and dirty English, for you monoglots (or polyglots who are not Teutonglots, a word we just made up):
By the end of 1939, Lieutenant Stahl, the technical officer at KG (Bomber Wing) 51, had made the proposal to defend bombers, and long-range reconnaissance airplanes, against attacking fighter aircraft, by means of flamethrowers built into the rear of the airplane. The attacking fighters would be caught in soot from oil smoke, so that their windscreens would be struck blind. In February, 1940, experiments with a Heinkel 111 and Junkers 88 took place at the Tarnewitz test center. The device was also used experimentally by KG 51 at the beginning of the Russian campaign, but does not seem to have actually been employed by the troops.
The last line of that paragraph addresses the second flamethrower developed by the Luftwaffe: “As an offensive weapon, the “Gero 11″ A, Block C was used by the FW190 for low-level attacks.” ["Gero 11 A Block C" is a reference to a Luftwaffe nomenclature model that sorted modified weapons into "Bunds" or batches, so we've translated it as "Block" as the USAF uses such as "F-15C Block 52," it's also like the US Navy's Mark X Mod Y nomenclature system].
Ganz einfach, as the Germans say.
The problems with the defensive flamethrower are obvious. It brings more inflammable material into the fuselage of the plane (the He111 and Ju88 were well designed, with the highly inflammable avgas being in the wings, giving the crews — who were clustered near the nose of the plane in both designs — a fighting chance at escape from a torched plane. Fear of fire was a very real thing for the WWI veterans who dominated Luftwaffe command in the years between the wars; the Imperial Air Service had been the first to issue parachutes to pilots in the Great War, and Nazi disregard of human life didn’t extend to the lives of expensively trained technical specialists like aircrews.
But the inflammability of the mixture aboard the plane is the least of it. The sooting-out-the-windows approach seems to depend on fighter pilots willing to cooperate by flying into the plume, or staying in it. In other words, fighter pilots with really crappy reflexes, a very small subset that is not likely to be effective at shooting down bombers in the first place. The defensive flamethrower just wouldn’t work 99 times out of a hundred. And worse, the long plume would draw attention to the plane. Air-war stories, from any war, are full of The One that Got Away because the fighter pilot lost sight of him. A plane trailing one length of fire and three more of black, billowing smoke would ring the dinner bell for every fighter for miles around.
Now one possible use might be to allow a plane to “play dead.” The idea being, to make the fighter pilot think, “Hey, I flamed him, let’s go find another target.” But the Germans don’t seem to have conceived it that way.
As far as actual flame effect on fighters, Lt. Stahl was too technically astute to suggest that. As you can see, the flame extends barely a planelength behind the hurtling bomber.
One gets the sense that some of these German development programs were followed not because they had hope of practical result, but because a a couple of engineers were taken with the technical challenge — the WWII equivalent of “sharks with frickin’ laser beams on their heads.”
The pictures are from LuftArchiv.de and we strongly suggest you spend some time there, particularly on the Bordausrüstung and Bordwaffen pages.
UPDATE: Turns out that it may have been more widely used that LuftArchiv.de thinks. This forum page contains a picture of a Ju88 of KG51, Lieut. Stahl’s unit, in Romania in 1941. The page also describes a combat use of a flamethrower by a Do17 of another unit, KG76,which is well documented by both the British attackers (who shot the plane down) and the surviving German aircrew. The Dornier was captured nearly intact; its disposition is unknown but it was probably scrapped during or soon after the war.
We’ll be uploading the photo of the KG51 Junkers’s tail area with a crewman, once we fix a small problem with the image file.