By Tommy H. Thomason

Thursday, May 31, 2012

Loading the Sting

They got to see the world but there was hard work along the way when your job was arming the airplanes:

Here, deckhands are loading a torpedo on a T4M-1 aboard Saratoga (CV-3) in May 1929.
National Archives 80G-21692

This is a 1,000-lb bomb being slung under a Marines Corps BG-1 dive bomber in February 1937.
National Archives 80G-216907

Being part mountain goat didn't hurt at times, particularly when the job was loading ammunition in the folded wings of a Grumman FM-1 Wildcat aboard Mission Bay (CVE-59) in January 1944.
 National Archives 80G-229237

But it wasn't all rough duty. Sometimes it was bombing up a Martin PM-1 seaplane at Pearl Harbor, Hawaii in October 1933...
National Archives 80G-216911

National Archives 80G-216914

Tuesday, May 29, 2012

Neptunus Lex is back

Carroll LeFon, aka Neptunus Lex, died two months ago trying to land a Kfir in below-minimum weather conditions at the only airfield he could reach with the fuel remaining. (Preliminary Accident Report) Among other things he left behind was one of the wittiest and thoughtful blogs on the interweb in my opinion. It has been off line for a few weeks but thanks to the efforts of one of his daughters, it is now back:

Sunday, May 27, 2012

Navy Joint Fighter Conference - October 1944

The Navy's Bureau of Aeronautics sponsored a Joint Fighter Conference that was held at NAS Patuxent River, Maryland on October 16-23, 1944. Representatives were invited from the Army, Navy, Marine Corps, Royal Air Force, Royal Navy, and Royal Canadian Air Force as well as from NACA and the manufacturers of engines/equipment and fighter aircraft like Grumman.

A large fleet of fighters was assembled for the pilots to evaluate:
General Motors FM-2
Grumman F6F-5, F6F-5N, F7F-1, XF8F-1
Vought F4U-1C, F4U-1D, XF4U-4
Goodyear FG-1*, FG-1A, XF2G-1
Lockheed P-38J, P-38L-5
Republic P-47D, P-47M
North American P-51D
Bell YP-59A, P-63
Northrop P-61
North American P-51D-5
Fairey Firefly Mk 4
Supermarine Seafire L2C, Seafire 3
DeHavilland Mosquito
Mitsubishi "Zeke 52"
*Bubble Canopy

More than one of some types was available on the line.

The manufacturers were eager to participate and put their best foot forward. Some of the airplanes were still in flight test or fresh off the production line. Here, an evaluation pilot poses in one such F4U. (The cut line in the Navy photo names him as Royal Navy Lt. J.P.M. Reid but as Bing Chandler points out in his comment below, facial hair rules this out; I agree that he resembles Commander Paul Ramsey.)

In addition, a Hoover Horizon in an NH (a single-engine, high wing, instrument trainer built by the Howard Aircraft Company) was available for flights. It combined the directional gyro and artificial horizon on one instrument along with a depiction of clouds above the horizon and trees below. Anti-G suits were provided for flights in airplanes with that capability. The F6F-5 was equipped with a lead-computing sight and an SNJ was assigned to be the target.

Each pilot (there were about 60 in all including Charles Lindberg) listed the airplanes that he wanted to fly and whether in daylight or at night. Daily flight schedules were prepared accordingly. What the pilot did during his flight was entirely up to him. The only obligation was to get the airplane back on time and fill out a two-page post-flight questionnaire based on what was looked at.

The only caution with respect to the operating area was to not bounce any airplanes in the Armament Test range south of the Patuxent River since "If pilots should jump an airplane there they might not be seen by the people operating turrets and the possibility exists of running into some complication along that line." 

For purposes of identification for this evaluation, each airplane was marked with a number on the mid fuselage behind or below the cockpit  beginning with an FM-2 that was 1. (The large number on some cowls in the photo above was the last three digits of the Bureau Number, often applied when an airplane wasn't assigned to an operational squadron.) The call sign was simply "Blue" and the evaluation number.

Here, Commander Paul H. Ramsey, Director of Test at NAS Patuxent River and chairman of the conference is climbing into Blue 24, a P-47 (the M according to the photo caption but a D according to the serial number). Note the gloves in hand, dress shoes, knee board strapped to thigh, and ear phones around the neck in lieu of a helmet. The life vest was recommended because there was a lot of water in the area.

Checkout, even by the standards of the day, could only be described as perfunctory. At the opening session, each contractor was given three to four minutes to describe their aircraft's "special qualities and restrictions, and general information relative to their use, speed, etc." Knee-board cards were provided that listed general data, the engine limits, and in some cases, airspeed limits and other cautions/restrictions. Each airplane was assigned a check-out pilot who stood on the wing and provided advice and counsel to the evaluation pilot until he had started the engine.

Here, McDonnell test pilot Woodward Burke is being given a checkout in the Zeke by Lt. C.C. Andrews, NATC project officer, Tactical Test, on the left with C.L. Sharp, a Chance Vought test pilot, on the left wing.

Report of Joint Fighter Conference: NAS Patuxent River, MD 16-23 Oct. 1944 was published by Shiffer Military History in 1998, with technical editing by Francis H. Dean. It is a compilation of documents and transcripts from the conference. It includes a memo to the BuAer Chief summarizing the results, the transcribed (including errors) remarks of the daily briefings and wide-ranging discussions, a summary of the opinions (qualitative and quantitative) for each type, etc. The Report is a fascinating time capsule of the status of U.S. fighter airplane capability, issues, and development as of October 1944. My favorite is the statement by a test pilot from Hamilton Standard who was answering a question about counter-rotating props: "Commander, after just flying the (YP-59A), I am out of business and I don't think there is any reason why we should talk about dual rotation. If anybody needs a good tug boat captain or something, that is about all I can talk about. I just finished the test in the squirt job and I have about two pages of comments. First I am going to hand in my resignation."

5 September 2016: Ted Dettman created a summary of the rankings (1 is best) from the data in the book:
The F4U comes out best overall based on this, but in action the P-51 was obviously good enough where it mattered, e.g. range, which isn't a figure of merit that was evaluated at this conference. The Navy considered buying a carrier-based variant of the P-51 late in the war ( but by that time, jet fighters were clearly the future so they bought what was arguably a jet-powered P-51 from North American instead.

A possibly apocryphal (but definitely plausible) anecdote that might explain two Navy airplanes being in the top three was that early on in the production of the F4U and the F6F, the Navy gave Grumman an F4U to evaluate and Vought, an F6F, suggesting more of the better airplane would be bought and maybe the one they were building wasn't it. Certainly the Navy had a practice of contracting for the development of two different airplanes for the same fighter mission, thereby incentivizing its contractors to do their best.

Sunday, May 6, 2012

Not as Easy as It Looks II

There was much for a pilot to learn in the transition from propeller-driven airplanes to jets and much to like about the new propulsion technology. One was power management. Jets had a throttle lever. Prop planes with powerful altitude-compensating engines had a throttle and also controls for the propeller rpm, mixture, cowl flaps, carburetor heat, alternate air, oil cooler and intercooler shutters, and the supercharger. Not to mention magneto, oil dilution, ADI (Anti-Detonant Injection) pump, and other switches. There were a few more gauges to monitor as well, each associated with one of the controls, whereas the jet pilot dealt with any engine issues with only the throttle.

This is the throttle quadrant of a Grumman F6F-5N Hellcat.

Although reciprocating engine power management was basically accomplished with the throttle and propeller controls, fighter pilots also had to control the supercharging of the engine based on altitude. Supercharging was necessary to offset the loss of power due to thinner air as the airplane climbed. Basically, the supercharger thickened the air by pressurizing it.

The following is from the F6F Hellcat pilot's manual.
The circled numbers 1, 2, and 3 refer to War Emergency, Military, and Normal power settings at the same gross weight. (The limits of continuous operation for War Emergency and Military were five minutes and 30 minutes respectively.)

The notches in the performance lines indicate the transition between the  supercharger (also known as blower or boost) settings, which were neutral, low ratio, and high ratio. Takeoff was accomplished at the neutral setting, meaning the air going into the cylinders was not being pressurized. Depending on the power setting (roughly normal, maximum cruising, military, and war emergency), the pilot would shift into low ratio at 7,000 to 13,000 feet and into high ratio at 22,000 to 25,000 feet.

To shift up to a higher ratio, the pilot had to reduce throttle to avoid exceeding manifold pressure at the increased boost. Shifting down was unrestricted although the pilot was cautioned, except in an emergency, not to shift less than five minutes after the last one to allow the dissipation of heat from the clutches. He was also warned to "never close the throttle even momentarily (and avoid any abrupt movement of the throttle) while operating in low or high blower." In addition, the use of supercharging at lower altitudes than necessary might result in surging in the induction ducting; the pilot was cautioned not to reduce throttle in that event but to immediately shift to the next lower blower speed "unless the tactical situation makes this undesirable"; open the throttle and reduce RPM; or shift to alternate air. Although the pilots of early jets had to avoid abrupt throttle movements in certain conditions to avoid the risk of flame out or compressor stall, their workload and attention to power settings was notably less in a combat situation.

But there was still more for the pilot of a propeller-driven fighter to keep in mind. War emergency power (WEP) was predicated on the availability of anti-detonate fluid (essentially a water and methanol mix) of which there was a 12-minute supply. All the pilot had to do was advance the throttle beyond the limit stop (at one point, this was a break wire) to close a limit switch that activated the ADI system. However, before that, he was advised to check the ADI fluid quantity gauge to insure there was water available and activate the ADI pump to clear the lines of air and build up pressure in the system (the tank was behind him, a long way from the engine). Continuous operation was not to exceed five minutes. If he was operating in low or high blower when the ADI fluid ran out, the auxiliary stage pressure regulator would control the manifold pressure to military power limits. However, this protection was not provided in neutral blower. If he did not pull the throttle back immediately, the result would be "serious engine damage, or total failure, within a few seconds." He also had to remember to turn off the ADI pump because it was not designed to run dry.

War emergency power shortened engine life but at low altitudes it provided about 500 feet per minute more rate of climb and 25 mph more speed. It doesn't sound like much, but in a well-known World War II incident, Ira Kepford used it to get out of serious trouble. He was alone, just above the water so he couldn't dive away, headed away from home and help, and had three pursuing Japanese fighters in position to shoot at him if he turned either left or right. Using WEP, he was able to open the distance between his F4U Corsair and the Japanese fighters enough to be able to turn back safely.

Automatic control of cowl flaps and supercharging was introduced with the Vought F4U-5 Corsair. However, it received mixed reviews because of the uncertainty when or if the system would actuate the cowl flaps or do a blower shift. In any event, by that time propeller-driven fighters were obsolete.