Flying wings

Flight Journal, Oct 2003 by Tucker, Charles, Quinn, J J

Controversy, truth and technology

JACK NORTHROP HAD GUTS. NO ONE ELSE WOULD HAVE DEVIATED SO RADICALLY-and on such a grand scale-from orthodox thinking, as evidenced by his flying wings. Even today, the designs have a "Star Wars" edge to them, but in 1947, they stretched imaginations-perhaps to the breaking point. The program cancellation was carried out with a vengeance: all existing airframes, except for the diminutive N-9M, were chopped up.

Today, Northrop's efforts can be seen in the B-2A, but the original program is cloaked in mystery and myth. The questions are many, and the answers are few. In the following pages, flying-wing test pilots Charles Tucker and J.J. Quinn tell us how the wings flew. Aerodynamicist Barnaby Wainfan discusses the technological aspects of flying wings, and historian/author Walter Boyne touches on the controversy surrounding the wings. Read on, and wonder what might have been.

Flying Northrop's Wings: a pilot's perspective

THE FALL OF 1947 FOUND ME DOING PRODUCTION TEST flights on the Lockheed P-80. This was not the sort of excitement that I was looking for as a test pilot, so I kept my ear to the ground, hoping to find something more suitable. I had been following the NACA and Air Force "X"-plane programs for the exploration of transonic and supersonic flight, and I thought I'd sure like to be involved with something like that.

It soon came to my attention that Northrop was looking for a test pilot for its X-4 tailless transonic research plane program. One of the main requirements of the pilot was that he not be taller than 5 feet, 8 inches because the X-4 was relatively small. He should also be slender and have jet experience. I fit those requirements handily, so I applied for the job.

Northrop hired me for the X-4 project, and I fell in love with the airplane the first time I saw it. The bad part was that it was still under construction and nowhere near being ready to fly, so the powers that be had to find something for me to do while I waited for the X-4.

I was put to work flying the company's Beechcraft 18-ferrying people and parts from Hawthorne to Muroc Army Air Field and wherever else people or parts had to be delivered. At first, I was somewhat disconcerted about this state of affairs, but events soon led me to some of the most exciting flying anyone could imagine.

THE N-9M

E.P. Hetzel was the flight-test engineer on the X-4 program. Since the X-4 would not be ready to fly for some time, E.P. thought it would be beneficial for me to fly the N-9M to become familiar with the format in which he wanted my written flight-test reports. E.P was a very good instructor-a stickler for detail and clarity-and he taught me much about writing flight-test reports that stood me in good stead during the years to come. He would assign me a dummy flight test (a repetition of a flight test that had already been done and for which engineering data had already been accumulated); I would fly and then write a flight report for it. He critiqued these reports with me and showed me why he wanted the data presented in a specific manner. In short, he taught me to write clear, concise, brief reports that the engineers would understand quickly and without questions.

The N-9M's wingspan of 60 feet was approximately one third that of the XB-35/YB-49's 172 feet. The N9-M aircraft were designed to test Northrop's ideas on all-wing aircraft as a proof of concept to build the XB-35. By the time I flew them, just about all the engineering data had already been gleaned from the N-9M program, but it was nevertheless a very valuable learning tool for me. I eventually logged about 40 hours in the airplanes.

The N-9Ms handled well but had a few little idiosyncrasies. One was that in any sort of disturbed air, the airplane displayed a low-amplitude, high-frequency pitch oscillation. This was because of low damping owing to its low tail volume. If flown at around 22 or 23 percent of the mean aerodynamic chord, the airplane wasn't unstable in any way; it just didn't damp well.

The airplane was virtually immune to the common problems encountered during crosswind landings. It was so unbelievable that a crosswind could have hardly any effect on an aircraft during landing that I used to look for runways with good, stiff crosswinds and land on them because it was so much fun.

Four N-9Ms were originally built. The first one crashed, but the surviving three were flown by many Air Force pilots. I flew all three N-9Ms, but I no longer remember how many hours I flew in which one. They were all pretty much the same, the major difference being their powerplants. Depending on the version, the aircraft used Menasco or Franklin engines of 260 to 300hp each.

The last three N-9Ms were the first aircraft built with a full-power, irreversible, hydraulic-power control system. One characteristic of the first manual-control-system N-9M was that during a high angle of attack, the large elevators tended to float upwards and move the stick back. If the pilot could not overpower the elevators and push the stick forward, it would be forced into his stomach and would pin him to his seat. This was the direct cause of Max Constant's fatal crash in the first N-9M. Evidently, when up-elevator was applied to initiate a stall, the elevators floated to the full-up position, and when the stick came backward, Constant wasn't able to force it forward to break the resultant spin, and he couldn't free himself from the seat to bail out. This trait was shared by some of the prewar European flying wings, and it caused a few crashes on that continent, too.