The first aircraft designed and built by James S. McDonnell’s new company, the Army’s XP-67, is one of the most unusually shaped aircraft of all time and also one of the least documented. Its combination of sheer curvaceous sexiness and a tantalizing (and frustrating) lack of photographic coverage have made it a cult favorite among aviation history buffs for decades. Attempts had been made to tap into the historical records of Boeing (merged with McDonnell Douglas in 1997), but the results were meager, to say the least.
We had retired from Boeing in St Louis and were looking for a project. We both love to investigate. What better challenge could we have than to try XP-67? We started by revisiting the Boeing Historian’s office, but found nothing new there. The National Archives and Records Administration was the next obvious place to look, and indeed there were a number of production drawings of parts in his collection. COVID disrupted our plans there, with NARA closed to visitors for as long as we were given to write an XP-67 story for Osprey Publishers’ X-Planes series. We had to find other sources, and fast.
Having made a number of contacts with individuals and organizations, we gradually began to piece together the XP-67 story that included a variety of photos and drawings that had never been published. This research continued to expand in scope, incorporating all sorts of factors that we hadn’t been aware of. Along the way we discovered many things that surprised us, since previously we only knew the first level story that has been repeated so many times over the years. Here are our top 5, and they may surprise you too:
1. XP-67 actually had a nickname! “Moonbat” wasn’t used at the time, but it’s completely understandable why it was kept loose for so long. The plane looks like a bat, thanks to the extreme mix of engine pods with wing and wing with fuselage. In conventional aircraft, the mix is much more restricted and is called “filleting”. The most distinctive external feature of the XP-67, then, is what led Army test pilots to give it a nickname in their official report: “The XP-67 is known as the ‘flying steak’; any longitudinal cross section through the aircraft is an airfoil section.
two. The XP-67’s engines weren’t particularly troublesome! And they were definitely not prone to catching fire. Contemporary records do not always make a clear distinction between overheating and actual fire, but in all but one case, those events were due to McDonnell Aircraft Corporation (MAC) designed peripherals, such as ducts and valves, rather than failures in the engines. Literally the only time an engine component failed and caused a fire was during the last flight of the XP-67, after completing 8 months of flight testing. It’s worth noting that the only other aircraft that flew with the same Continental I-1430 engines was Lockheed’s XP-49, and there were no fires or serious mechanical failures either. It has been said many times that they were unable to deliver their full rated power, leading to slow launch and high speed performance. But in fact, an Interoffice Memorandum dated January 19, 1944, so early in the program that flight testing had barely begun, the Army’s program coordinator for XP-67 to the Chief of Aircraft Projects at Wright Field noted that as a result of extensive testing of the engine on the full-scale nacelle fixture “it is the opinion of this office that the engine has performed satisfactorily. This view is confirmed by full-scale gondola tunnel testing at Wright Field, during which engine difficulties were virtually non-existent. [sic] and the engine delivered its rated 1,600 hp for long periods of time.” Later in the show, when rumors of fires apparently began to spread, Wright Field’s Chief of Technical Staff noted that apart from a fire on the first flight (resulting from the failure of a duct carrying exhaust gases, nothing to do with the engine itself) ) – “The fifth flight took place on March 25, 1944. Approximately fifty flights have been made and no serious functional difficulties have been encountered.”
3. Army pilots only flew XP-67s a few times! Virtually all of the XP-67’s test flights were flown by MAC chief test pilot Ed Elliott. Three Army pilots flew a total of only five flights and a total of about 4 hours split between them, barely enough time to become familiar with the aircraft, let alone make more than cursory judgments about its performance. Some of his criticisms are puzzling, such as comparing the maneuverability and turning radius of the large twin-engine XP-67 to that of a small single-engine P-51B, and naturally finding the latter to be superior, a complete irrelevance since the XP-67 it was intended to destroy bombers with its six 37mm cannons (never installed) rather than dogfights with enemy fighters. There are indications in surviving program correspondence that other Army pilots may have flown individual flights on occasion, but they appear to have been opportunistic rather than part of organized testing activities.
Four. The launch and final demise of XP-67 happened very close to each other! McDonnell’s facility at Lambert Airport in St. Louis was on the north side of the field, and that’s where the XP-67 was launched in November 1943. On a windy day in September 1944, it made its last flight, it landed in flames and was abandoned. by his pilot on a taxiway in the southwest corner of the airport, less than 1,000 yards from where she had been deployed. We obtained permission to enter the perimeter of the current St Louis Lambert International Airport and stood at both sites, which were easily visible to each other.
5. XP-67 was not the only “X-fighter” at Lambert Airport in 1943-44. The McDonnell facility was just across the track from the huge new plant that Curtiss-Wright had built to primarily build variants of the SB2C Helldiver family. At the same time as the XP-67 was being developed, Curtiss-Wright was building their XP-55Ascender, which they launched in July 1943, just 4 months before the XP-67 first appeared, and was lost in November 1943. while flying. from Lambert, just two weeks before XP-67 left the assembly building. The second XP-55 saw the light of day in January 1944, while the XP-67 was in the process of making its first four flights from Scott Field in Illinois. But the XP-55 number 3 came out in April 1944, while the XP-67 was being actively tested by flying from Lambert. It is very likely that both aircraft were in view one or more times, but sadly no photos have been found to prove this. This near neighbor of two WW2 Army X Fighter Planes is one of a kind!
Those were some of the most interesting things we discovered while researching and writing our book. But on a personal note, what isn’t mentioned is the fact that much of the test flight of the XP-67 and XP-55 as well, including (we think) the final catastrophic flight of the XP-67, took place directly in the airspace. about our house! At that time it hadn’t been built yet, of course, but it’s still something we like to imagine when we look up at the sky.
– Steven Richardson was an aeronautical engineer who worked at McDonnell and Boeing, and Peggy Mason was in communications at Boeing. He can request his book McDonnell XP-67 “Moonbat” (X-Planes) here. Check here.