When I was a pilot and maintenance officer in a carrier fighter squadron, I used to wonder how our airplanes became a part of the U. S. Fleet. Some types were thought of with affection, some with healthy respect, and a few aroused only trepidation or disgust. Since then, a tour of duty as a flight test pilot at the Naval Air Test Center has opened my eyes to a tortuous, time-consuming process that makes an experimental aircraft into a satisfactory fleet replacement. Let’s open the diary that a naval flight test pilot might keep and trace a typical evolution of a carrier fighter, the realistic but fictitious XF12K “Monsoon.”
May 12, 1950
This morning I was assigned to the XF12K project. I spent the day in the voluminous project files of progress reports, detail specifications, contracts, and wind tunnel reports, and I found the outline of a very hot airplane. The XF12K has 35 degree swept-back wings and tail, completely hydraulically-powered controls, and tips the scales at 35,000 pounds. Its power comes from the untried J-54 turbo-jet, a 7600 pound thrust engine built by the Hunter Engine Co. After-burning increases static thrust to 9700 pounds, which is reputedly enough to get the airplane to 50,000 feet in 5 minutes. It has a tail hook on it, for the time being, and is supposed to operate off a carrier in any sort of weather. On the basis of wind tunnel data, it is supposed to have good transonic and supersonic characteristics.
I noticed that the detail specifications for the airplane were dated nearly three years ago, with the contract dated in January of 1948. The company progress reports gave the date of the first flight of the first of three prototypes as November 17, 1949. Since then the No. 1 prototype has been flown 114 hours by company test pilots. We received a phone call from the Bureau of Aeronautics, for whom we work, and were told that the No. 1 prototype is almost ready for its first Navy evaluation.
May 24
The Senior Project Pilot, Commander Worth, and I spent the afternoon planning and coordinating the lines of investigation each of us would follow when we make the first evaluation flights in the “Monsoon” tomorrow at the plant of the Kerry Aviation Corp., the builders of the beast.
May 26
Now I know about what will keep the well-equipped fighter pilot of tomorrow in business. In two days Cdr. Worth and I flew the XF12K for a total of 13 hours. The taxpayers have their money on a winner this time, but a lot of work must be done on the airplane before it is ready for the big time.
We spent several hours last night composing a dispatch, reporting the results to the Bureau of Aeronautics. The full story doesn’t get into such a dispatch. The part that didn’t get in was the impressiveness of the lunging take-off, the exhilaration of riding almost 10,000 lbs. of thrust, the feeling of being a comfortable part of an airplane that a well-designed cockpit gives, and the sense that the airplane was built for the pilot. Those items don’t win air battles and protect the pilot from a high accident rate, so the Bureau is not interested in them. The part of the story that did get into the dispatch is going to shake up the Bureau’s Fighter Design Desk a bit. What they heard from us was this:
(a) Inadequate elevator control to stall the plane off the runway or lift the nose wheel off the runway before attaining 110 knots on take-off.
(b) Poor directional stability. The airplane snakes badly in rough air or after any directional disturbance.
(c) The artificial “feel” built into the stick and rudders to replace the normal air loading eliminated by the hydraulically- powered control system was too unrealistic, causing a strong tendency to over-control.
(d) Extension of the landing flaps caused a sharp nose-up pitch.
(e) The elevator surface flutters at approximately Mach .93.
(f) Instead of having to pull harder to tighten a steep turn or make a sharper pull-out, the stick force required lessened.
(g) Very poor rolling velocity around Mach 1.0. It was the first time I had exceeded the speed of sound but it didn’t require experience at Mach 1.0 to feel the airplane stiffen up laterally.
(h) Mach No. characteristics were satisfactory in the supersonic range but marginal in the transonic range.
There were several other items, mostly minor ones. The Kerry test pilots knew these characteristics, but most of these items are critical because of the “Monsoon’s” future as a carrier fighter, a future for which the civilian test pilot can not evaluate the airplane. The final measure of a combat plane comes from a combination of a trained test pilot and an experienced fleet pilot, an officer who can mix the salt with the salad.
May 28
The Bureau acted promptly on our dispatch. A phone call ordered Cdr. Worth and me to Washington yesterday where we met with all of the interested people. The head of the Piloted Aircraft Division ran the meeting. Representing the Navy were several officers and civilians from Fighter Design, Military Requirements, Design and Engineering, and Aero and Hydro offices. Representing the contractor was the Chief Engineer of Kerry with the Kerry test pilot and the project engineer for the XF12K. Each of the reported deficiencies was worried to bits by the Navy and the contractor. After everyone had established the effect of each discrepancy on operational hazard, delay to the program, cost involved to correct, etc., the meeting broke up with Kerry promising to eliminate the deficiencies and to keep the production line building up.
June 28
After over 4 weeks, Cdr. Worth and I were ordered back to the Kerry plant to check on the progress of the fixes. Several minor items had been cleaned up. We reported increased elevator control, directional stability improved by lengthening the tail fin, slightly better “feel” in the stick, but no real major progress. I have a suspicion that it is the Navy that is being tested at this point. I know that some of the deficient items can be fixed up, although major modification and expense might be involved. There seems to be a possibility that Kerry is trying to find out exactly how strongly we feel about some of the items that seem borderline to them. This is something that will have to be thrashed out in conference.
June 30
The Bureau project officer came to Patuxent today to discuss the XF12K with us. He said that the Fighter Design desk intended to stick to its guns until Kerry could deliver a completely satisfactory airplane, since the Navy didn’t have the money to spend on second-rate machinery. It is very encouraging to a test pilot to have the front office stand behind him, for the plane he is testing today will be the combat plane he flies in a fleet squadron tomorrow.
In three weeks the No. 3 prototype will be ready for us to bring to Patuxent for an evaluation in all phases of its intended use. I have prepared a program designed to scrutinize the most items in the shortest time. I will be allowed only one month to complete a program covering catapult and arresting gear workouts, stability and handling characteristics, and a very brief look at the climb performance. Only with the best cooperation from the maintenance department, a break in the weather, and a lot of luck will that be possible.
July 22
Today I ferried the No. 3 XF12K from the Kerry plant and turned it over to our weight and balance people. The airplane was shy about 1400 pounds of its combat operating load (35,000 lbs.) so time must be spent bolting ballast into the fuselage. All of the instruments must be calibrated by our instrumentation section. Since this project will be only a brief evaluation, no special instrumentation will be installed. I hope I can get all of the required information on my knee pad. An “A” priority has been assigned to this phase of the project because the production line is beginning to bulge at the seams. After this series of tests, it will become increasingly expensive to have a bad characteristic corrected.
July 28
At long last, I finally got the airplane back after its tour through the hands of the instrumentation, the weight and balance, and the maintenance sections. They are all trying to do their jobs right, but it is a strain waiting to get started with people in the Bureau and at Kerry wondering why you don’t get some information to them. The Kerry Corp. has sent six very expert maintenance men with the airplane and the project is getting a tremendous boost from their efforts. Needed spare parts are described directly to the factory by telephone or teletype, received by airmail, and installed that night. It is of some comfort to know of the vast resources behind me, but it is the producing officer that earns the wage, not the comforted one.
August 4
I have been trying for four days to get an airspeed calibration on the speed course. I try to get airborne right after daybreak when the air is the smoothest, but the air has always been too rough. In the meantime, I have been making measured take-offs, practiced carrier landings, and paced stalls with a TBM trailing an airspeed pick-up at the end of a long cable, well clear of the disrupted airflow around the airplane. The catapult and arresting gear crews have been busy with the data figuring out what it will take to handle the airplane in the gear. Tomorrow we must start the catapult trials and hope to get an airspeed calibration later.
August 11
After more hours at low altitude and low speed than I care to think about, the carrier suitability phase has been completed. It became obvious early in the trials that the “Monsoon” would have to be modified before any extensive work could be done on the catapult or the arresting gear, but the deficiencies do not appear serious. All tests were covered by high speed cameras from several angles and the film is now being studied by Kerry and Navy engineers. Several off-center landings upset me and nearly upset the airplane, which rolls badly after picking up the wire. This may mean that a roller-head hook will have to be used, which would require an oscillograph with strain gage pick-ups at various critical points in the tail section. The time required to complete a project increases very rapidly with the complexity of the instrumentation, but sometimes there is no choice. We have to know that the tail will stay on the airplane under sustained carrier operations.
The catapult tests opened up a very disquieting possibility. Unless the production J-54 jet engine produces more thrust than this one, the XF12K is not going to leave the ship with enough extra airspeed to blow out a match. I took a dozen maximum- charge catapult shots during the tests, and I was mighty happy to have a runway ride in front of the catapult instead of a one-way ride in front of a ship.
August 14
We had another conference at the Bureau, involving everyone we usually have plus the Ships Installation delegation. Ships Installation was interested in hearing about the XF12K in its carrier trials, because they are responsible for providing adequate facilities and equipment aboard ship to handle the airplane. We gave them the data on the catapult launches, but their crystal ball rang the bell on that angle. They told us that a contract had already been let to modify the carriers which might be expected to handle the F12K.
The conference broke up with the F12K on a considerably firmer footing as a probable standard fighter plane of the future. The design is proving to be a basically good one, and the Kerry Corp. appears to be willing and able to adjust the design to fit the Navy’s requirements. Tomorrow I start the lonely job of testing characteristics at high altitude and high Mach No.
August 22
We sent a speed letter to the Bureau reporting very bad “Dutch rolling” in rough air at high altitude, neutral elevator control force stability between Mach .9 and .95, very poor rolling velocity at airspeeds above 600 knots, ineffective speed brakes, and fuel slosh.
There were other minor items of cockpit design, failures of various components, and bad design of some components which had already been reported by Yellow Sheet directly to the Bureau’s Board of Inspection and Survey. These Yellow Sheets report a deficiency, recommend a correction, and specify its importance. I have already received copies of the contractor’s proposals for correcting some of these minor items. The more important deficiencies must be ironed out in conference.
August 24
We had another conference on handling characteristics at Patuxent. There was a little difficulty because the contractor claimed that some of the handling characteristics which we said were unacceptable were actually satisfactory as far as the stability specifications were concerned. The stability specifications were written to act as a guide for the contractor and to provide a minimum standard by contract. If some characteristic doesn’t meet specifications, the contractor must fix it at his own expense. If a characteristic meets specifications but the Navy test pilots still find it unsatisfactory, the contractor fixes it, but the Navy foots the bill. After the Kerry vice-president had argued out which deficiencies were not his responsibility, he was asked to correct them all and everyone was happy. I was told to ferry the airplane back to Kerry so that it could be worked over at the factory. Kerry estimated that the first production airplane would be ready in approximately two months.
We also advised the Bureau that XF12K required 8.5 minutes to climb to 50,000 feet which is far from the guaranteed performance. The Bureau is concerned about it but must wait until a production J-54 engine is available for test before anything can be done about it.
November 10
For the past two months I have been making periodic trips to Kerry to check their fixes on the troubles we found. A great deal of progress is being made on the prototypes but some of the production planes will be built before all of the modifications can be incorporated in the production line. Two other pilots from the office who have never flown the XF12K are going to Kerry with me Monday to fly the production version, the airplane with the most fixes that can be incorporated before delivery. The Bureau must make a decision now whether the Navy should permit the airplanes to be delivered to the fleet “as is.”
November 13
Our evaluation advised the Bureau by dispatch yesterday that the present production version of the F12K was not satisfactory but was acceptable for service operations since none of the remaining deficiencies were safety-of-flight items. We recommended that the airplane be restricted to VFR conditions until the poor control force harmony at slow speeds is corrected. If our recommendation is accepted, it won’t be necessary to stack new F12K’son the Kerry field while solutions to the remaining problems are being worked out.
November 20
The Bureau accepted our recommendation. I picked up the No. 1 production model yesterday and it is due for extensive testing. Top priority will be assigned to the climb tests. Our instrumentation section has been working for several weeks designing and building a photo-panel, oscillograph, and other instrumentation which must be installed in the F12K to get reliable figures.
December 21
Since I picked up the airplane, it has been weighed, ballasted, and thoroughly instrumented. After a long frustrating wait, I shall be able to make my climb and level flight runs with a photo-panel recording everything required to compute accurate fuel consumption and performance information on the basis of a standard day. In addition, I shall be able to tell where every control surface was and how much force was required to maneuver the airplane for every second in the air. I don’t need that information on control deflections and control forces to tell whether the airplane is satisfactory or not, as far as I’m concerned, but if I say the airplane is unsatisfactory, the information will be available to indicate exactly why and how it was unsatisfactory.
December 30
The photo laboratory gave me a Christmas present of the photo-panel record of 3 timed climbs to 50,000 feet which I made on Dec. 23. Nothing but bad news. A temperature inversion in the atmosphere at 37,000 feet ruined the most important parts of the climb. Fortunately I have been able to find smooth air at several altitudes so my level flight test program is proceeding satisfactorily. I hope to mail a preliminary report of fuel consumption in a month.
January 11, 1951
I flew the Kerry experimental “Dog Ship” today which had the latest aileron and speed brake configuration. They finally resorted to spoiler ailerons, which I dislike in principle but liked in practice. Kerry field representatives will install the new ailerons and speed brakes in all “Monsoons” already delivered.
January 31
We have been in constant touch with the Bureau on the unexpectedly low take-off performance and rate of climb. Our thrust stand test indicates that the engine does not deliver guaranteed thrust. The Hunter Engine Co. announced today that they have made a few modifications in their engine which will allow it to deliver more thrust. I am going to Kerry tomorrow to fly a modified engine.
February 26
After making 74 arrested landings and 50 catapult shots on the field, we have been ordered aboard a carrier for the actual carrier trials of the F12K. The modified J-54 engine proved to be the answer. Climb and take-off performance is now acceptable and all engines in service are receiving the necessary modifications from Hunter field representatives. Last week I went to Kerry to fly their “Dog Ship” which was modified to correct the snaking and longitudinal stability at Mach .93. A “black box” cured the snaking and a weird tab arrangement cleaned up the longitudinal stability. Retroactive service changes have been ordered and modification kits will soon be going to the fleet.
March 9
The carrier trials were eminently satisfactory. I made 30 landings and catapult launches with less sweat than I saw on the brow of the Kerry vice-president who observed the trials. Nothing stands in the way of an unrestricted certification of the “Monsoon.” I saw the monthly report of the other test divisions at Patuxent today. The accelerated service test is about completed with all of the information about maintenance that was gathered in 300 hours of night and day operation already in the hands of fleet maintenance officers. The bugs in armament and electronics have been nearly eliminated. Tactically the airplane appears to be more than equal to any expected opposition.
So ends the first phase of the “Monsoon’s” evolution. It is only a phase, for in the succeeding months the test airplanes at Patuxent will be used to increase the versatility of the plane, test new devices for safety and effectiveness, and improve the maintenance, armament, and electronics. Different fuels, engine modifications, redesigns, all will be scrutinized for fleet application. Although the Monsoon is now an effective weapon, a year from now it will be even better.