By Tommy H. Thomason

Thursday, July 28, 2011

Halcyon Days

Click Here for 23 minutes of footage taken aboard CV-59 Forrestal during its shakedown with ATG-181 in February/March 1956, courtesy of the video library of the San Diego Air and Space Museum.

The Air Task Group, tail code I, consisted of:

VF-41 Black Aces F2H-3 1XX
VF-21 Mach Busters FJ-3 2XX
VA-86 Sidewinders F7U-3M 3XX
VA-42 Green Pawns AD-6 4XX

Detachments were:
VAH-6 (NH) Det 42 Go-Devils AJ-2 XX
VC-12 (NE) Det 42*          AD-5W 7XX
VC-33 (SS) Det 42 Night Hawks AD-5N 8XX
VC-62 (PL) Det 42 Fighting Photos F2H-2P 9XX
HU-2 (UR) Det 42 Fleet Angels HUP-2 XX

*Possibly not in any of the footage

There are a number of transitions to be seen. For one thing, some aircraft are blue and others in the same squadron are grey/white. (The F7Us are still in the experimental "unpainted" scheme.) Click Here for some background on the color scheme change that was decreed a year earlier.

One of the grey/white AD Skyraiders has a black-painted area where the exhaust stains would have otherwise been evident. This was typical of gray/white USAF A-1s in the Vietnam War but I'd not noticed it before on a Navy AD.

Another transition example is that the pilots are still using the flat approach to a cut as directed by the LSO, not the descending approach using the mirror landing system. In one segment, an F2H is on short final with another close behind.
Too close, perhaps, because the LSO can subsequently be seen waving off the second Banshee.

All but one of the FJ-3 landings are with the canopies closed as would subsequently be the practice.
The F2H and F7U pilots all have their canopies open for landing. Although open canopies for carrier takeoffs and landings had been standard since canopies were introduced, this became pilot's choice on straight-deck carriers at some point following the addition of the barricade (click Here for a description of the barriers and the barricade) after an incident or two when the upper strap of the barricade went into the cockpit of a crashing jet. Note that the FJ-3s are taking off with open canopies.

Why are the F7Us in an attack squadron, particularly since they are supposedly the Sparrow-missile armed Ms? The answer is probably that the Navy was transitioning to jet attack and had F7U-3Ms excess to their fighter requirements. Note that in the F7U wave-offs (both of which appear to be from too high a start) and the bolter, the Cutlass hooks are not down. This was a familiarization process building up to the first trap: the approach was the important part of the maneuver and more could be fit into a flight period if there were no traps in between.

The deck runs made the launch a lot quicker but were only practical with propeller-driven airplanes. (The white stripes at an angle to the dashed stripe led to the bow catapults.)

However, it appears that the A3D and A4D were qualified with JATO to allow them to make deck runs if the catapults were down the nuclear strike was called for. An F4D pilot also made a successful deck run, off a British carrier, after he unknowingly lost his catapult holdback capability upon launch from Saratoga to land aboard Ark Royal. Click Here

The F2H-3/4 Banshees had a nose gear that extended for launch. This (and the steam catapult) mostly made up for the fact that they were heavier than the F2H-2 but had the same wing and engines. Note the difference between the attitude of this Banshee about to be launched and the ones in the picture above.

The FJ-3s were started and taxied forward to the bow catapults with the FOD screen in place.

Lots of other details of carrier operation can also be seen, like the little three-wheel self-powered start carts as well as a contrast between the personnel cranials and float coats used today versus their absence then. The use of catapult straps and a separate holdback as described Here instead of todays nose launch arrangement is also noteworthy.

Thursday, July 21, 2011

Block Designation Letter

Occasionally, someone notices that the Bureau Number marked on some Navy aircraft is followed by a letter, usually lower case, and wonders what that is all about. This practice dates back to at least the late 1950s.

U.S. Navy aircraft were usually purchased in annual batches. There were almost always changes (improvements, problem fixes, different avionics, etc.) from batch to batch or even within a batch, which meant that there were groups of aircraft that were slightly different configurations, but not so different as to justify a change in the designation dash number. From a manufacturing configuration control standpoint, these were referred to as blocks. The maintenance documents provided to the Navy provided a cross reference of Bureau Numbers for each block for initial configuration definition and subsequent control. For convenience, the blocks were designated by letters, with A being assigned to the first one, B to the second, and so forth. Although not the usual practice in these matters, the letter "O" was not skipped for the 14th block as shown here.

However, aircraft were updated and improved during periodic overhauls based on time, usage, or accidents. Aircraft from the same production batch did not necessarily go through overhaul at the same time. Since changes continued throughout the life of the aircraft, that meant that the configuration of an aircraft that had been produced in a particular block began to diverge from others in that block. As a result, the block designation letter was not as meaningful from a configuration definition standpoint after the first overhaul or so and not necessarily put back on when the aircraft was repainted, as on this post-1962-designation-change F3H.

Also, not all manufacturers seem to have followed this practice. However, it was common on airplanes from Douglas and McDonnell.

Friday, July 15, 2011

One Hundred Years of U.S. Navy Air Power

Recommended reading:
The title says it all. Sixteen chapters including an introduction and conclusions by Douglas V. Smith. Thirteen different distinguished authors besides Smith, each published elsewhere in their area of expertise. Heavily footnoted. I learned a lot and so will you.

Sunday, July 10, 2011

Look! No Hands

What was actually only the latest in "hands-free" carrier landings was accomplished on 2 July aboard Eisenhower by an F/A-18D Hornet "modified to emulate an unmanned aircraft"
The unmanned aircraft being emulated is the Northrop Grumman  X-47B, which is currently in flight test and scheduled for at-sea carrier-suitability testing in 2013.

As it happens, the hands-off carrier landing capability has been around for a long time, with the first aboard a carrier being accomplished more than 50 years ago and used operationally since 1965. However, the X-47B system has to provide greater functionality—for example a hands-off bolter (a touch down with no arrestment)—and much greater reliability. since there is no pilot to take over when the electrons and ones/zeros begin to lose their way.

The impetus for a hands-off system in 1950 was the desire to minimize the shortcomings of jets with respect to all-weather operations and the amount of time that a carrier was unable to operate aircraft due to ship motion or ceiling/visibility. In those days, before inflight refueling, jets were unable to wait out poor weather due to their limited endurance.

Bell Aerospace won a competition with Honeywell and began developing the system in the early 1950s. It was ship-based, with a computer using radar data to determine the airplane's location relative to the glide slope and then sending corrections to the airplane's autopilot to alter its flight path to fly to and on the glide slope at the proper approach speed. All the pilot had to do was fly the airplane through an imaginary gate four miles aft of the ship on final approach and verify that the airplane was being guided by the ALCS, All-weather ( or Automatic) Carrier Landing System.

The first automatic landing of the Navy test airplane, a Douglas F3D Skyknight, took place in May 1954 at the Niagara Falls Airport, New York.
One addition required to the airplane in addition to an auto throttle was a corner reflector, seen above just in front of the nose landing gear doors, to insure the best possible radar data for the ship-based system.

Part of the interval between the successful demonstration at Bell and the first landing aboard a carrier was dedicated to developing a ship-motion compensation capability. During the last 12 seconds before the touchdown, ship motion was included in the computations;  a second or two from touchdown, the corrections to the autopilot ceased and it simply maintained pitch and bank.

The first at-sea demonstration was on Antietam in 1957. At the time, the system was housed in large vans and not ready for deployment in the operating environment aboard an aircraft carrier. Redesign and environmental (shake, vibration, EMI, etc.) qualification testing was required now that proof of the concept had been demonstrated.

A production contract was finally awarded to Bell in March 1960 for the SPN-10 ALCS. NATC accomplished the first fully automated landings with the production system in June 1963 on Midway with an F-4 Phantom and an F-8 Crusader, modified for the capability. However, another round of development and improvements were required so the first operational use was delayed to late 1965, when operational evaluations were accomplished with F-4Gs, ALCS-modified F-4Bs, aboard Kitty Hawk. The capability was subsequently retrofitted to F-4Bs and incorporated in new production F-4Js. After a Vietnam deployment aboard Kitty Hawk with VF-213, the 11 surviving F-4Gs (one was shot down) became F-4Bs again. (Either the Navy's F-4G's existence was forgotten/considered irrelevant or used to disguise the purpose of yet another F-4 variant, the Air Force F-4G Wild Weasel.)

The radar reflector on the aircraft was substantially reduced in size and made retractable. On the F-4, it was attached to a door that opened just forward of the nose gear.

On the F-111B, it was mounted on the upper link of the nose gear torque scissors so it deployed into position when the gear was down in flight.

When the system was working, the performance was brilliant, the airplane coming down the glide slope toward a three-wire arrestment like it was on rails. As might be expected from the vacuum-tube-based technology of the time, however, reliability proved to be a problem. A field change was made to improve SPN-10 reliability but at the expense of its automatic touchdown capability: the pilot had to take over at weather minimums and make the final corrections before touchdown.

In 1966, Bell received a contract to "digitize" the system with solid state electronics and computers and restore full functionality. The redesigned system was designated the SPN-42. A subsequent improvement, the SPN-42A, incorporated an X-Band radar for better system performance in heavy precipitation. It was operationally approved in 1968.

Development of the next ALCS generation, the SPN-46, was begun in 1980 to take advantage of advancements in  gyro, computer, and radar technology. It was declared operational in 1987 after an operational evaluation involving Kennedy and F-14s. It is being continually improved but will eventually be replaced by a GPS-based system being developed as a joint service program, JPALS (Joint Precision Approach and Landing System).