The Cold War ended more than 20 years ago and things like this still make me realize just how much things have changed.
SPANGDAHLEM AIR BASE, Germany – The U.S. Air Force launched the final A-10 Thunderbolt II tactical sortie in Europe at Spangdahlem AB May 14, 2013.
The airframe belongs to the 52nd Fighter Wing’s 81st Fighter Squadron, which inactivates in June.
“I’m proud to be a part of the last sortie,” said Lt. Col. Jeff Hogan, 81st director of operations and a pilot from today’s flight. “It’s definitely a sad day for the (81st) as we end 20 years of A-10 operations here. I’m just proud to take part in this historic event.”
The A-10 has been a Cold War icon in Europe for over 20 years and was originally deployed to stop the hordes of Soviet armor across the Fulda Gap in then West Germany (amongst other places).
I’d always pictured that operations would look something like this:
On a side note there’s, as of yet, there is no comment from DoD on whether or not the 81st Fighter Squadron will be reactivated and deployed to counter the “cat-tank” threat that has recently emerged in the Chicago loop (the vid was sent to me by a friend as I was working on this post. She works here.).
One of the few squadrons tasked strictly with the air-defense mission, JG-71’s Phantom days go back to 1974 and were one of the Luftwaffe fighter squadrons to fulfill NATO QRA duties over the Baltic and Iceland. On 8 May 2013 those Phantom days came to an end.
JG-71 Phantom Patch
JG-71s F-4F in the commemorative paint scheme to celebrate transition to the Typhoon
From 2010 to 2013 JG-71 flew both the Phantom and the Eurofighter Typhoon. This month they’ve said auf wiedersehen to the Phantom.
In the foreground, JG-71s Typhoon being escorted by a pair of their F-4F Phantoms
It’s been a fun ride.
JG-71 F-4F Phantom patch…with attitude.
[Updates]: Photorecon has some photos and a short JG-71 Phantom history.
Also, the “official” site for the Phantom retirement is here (in German). Lot’s of cool geedunk there if you’re so inclined.
There has been a lot of interesting books to come out about the Red Air Force after the Soviet World War 2 archives were opened up. Don’t tell anyone that I’m supposed to finish a book review for that…
Aerial delivery tests, as part of further operational demonstrations were conducted at China Lake, CA using dummies for static-line drop tests. Cargo drops with 5000lb to 20,000lb were also conducted from an altitude of about 4750ft. The heaviest drop was a 28,243lb load of CDS containers. The primary result of the drop tests found the troop door was too narrow.
The YC-15 also tested mid air refueling as both a tanker and receiver in May-June 1976. 102 hookups were made with a KC-135. Fuel transfer to the receiver was found to be slow (partly because the UARRSI was not designed for the aircraft). Trails of the YC-15 potential tanker aircraft used Navy and Marine Corps aircraft fly a position slightly below and behind the aircraft to simulate the probe-and-drogue method of aerial refueling.
One of the YC-15 aircraft receives fuel from a USAF KC-135.
A YC-15 acts as a tanker with a Navy F-14 Phantom flying in the “tanker-box.”
On 15 to 17 December 1975 YC-15 876 tested ground loading of Army vehicles.
An AH-1 Cobra being loading aboard a YC-15.
A McDonnell Douglas advertisement for the YC-15 showing an M-109 at the rear cargo door.
Overall the YC-15 was found to be a good airplane but had marginal maintainability. 2 of the biggest issues were was engine maintenance and the flight control system. Naturally the YC-15 was going to have maintenance issues because it, like all research aircraft, was intended to test technology and not necessarily representative of an optimized “production-type” aircraft (I remind the reader to a look at the differences between the YF-22 and F-22). Phase 1 tests ended in 18 August 1976. By then both aircraft accumulated 226 flights over 472.8 hours. The YC-15 demonstrated an ability to fly as slow as 62kt to a fast as Mach .78. The initial phases of flight test validates EBF as a valid solution to the STOL problem.
Phase II of the AMST program for the YC-15 began on 7 September 1976. Both aircraft underwent a number of modifications including having a CFM-56 turbofan engine installed on the #4 engine pylon. The wingspan was extended by 22.3ft as a result the wing area went from 367ft2 to 2107ft2! A fighter-type stick was also installed.
Previously shown picture of the YC-15 showing the installed CFM-56 engine on the #4 engine pylon.
On the software side, aircraft 876 had a number of modifications installed including a thrust management system (required because of the increased thrust of the CFM-56) (TMS), an Engine Failure Detection System (EFDS), a digital SCAS and the VAM was improved with a flight director indicator.
Phase 2 testing resumed 12 February 1977 and resulted in 49 sorties for 125.6 flight hours. 876 also went on a tour to NATO member nations in Europe.
In Phase III testing aircraft 875 was returned to original configuration but had a Gross Weight Selector (GWS). The GWS would calculate the optimum flap angle for a given gross weight at various flight conditions. The DLC was improved to operated with and engine out on final approach. All these modifications (including the increased aspect ratio of the wing) resulted in a 10kt reduction in approach speed. The final tally for Phase III testing included 416 flights over 796.3 hours total for both aircraft.
By February 1978 both YC-15s were placed into storage at Edwards AFB.
Part IV will detail the technological contributions the YC-15 made to the C-17 program and the return to flight of the YC-15 in support of that program.
Part one is a general description of the YC-15 aircraft. You can view that here. This post will detail the flight test program of the YC-15.
There were 2 YC-15 aircraft,serials 72-01875 and 72-01876. 875 was rolled on 5 August 1975. The first flight was 26 August 1975. 875 flew from the Douglas plant in Long Beach, CA to Edwards AFB. The only problem during this 2.5 hour flight was a landing gear door found to be ajar. The flight itself was therefore speed limited to 200kts at 20,000ft.
875 flew 3 times over the next 3 days, conducting general flight envelope verification and expansion tests. A further 2 weeks were conducting 7 air-worthiness flights. On 12 September, 875 moved to a Douglas Aircraft Company (DAC) test facility at Yuma, AZ.
876 flew for the first time on 5 December 1975. This flight took the aircraft from Long Beach, CA to join 875 at Yuma AZ.
The YC-15 Joint Test Force (JTF) personnel from the Air Force Flight Test Center (AFFTC), Air Force Test and Evaluation Center (AFTEC), McDonnell Douglas, Boeing (for the YC-14). The (Air Force Logistics Command (AFLC), Tactical Air Command (TAC), Army and the USMC played minor logistical roles in the flight test program. NASA also sent (short take-off and landing (STOL) engineers to analyse data gleaned in the AMST program. The core pilot cadre for the YC-15 was made up of 3 contractors, 3 AFFTC and 3 AFTEC pilots. The competing aircraft were housed in separate hangars with the JTF office between the 2 contactors. This became the model for both the ATF and JSF programs.
The consensus amongst the test pilots and crews was that the YC-15 had generally good handling qualities. The aircraft was easy to fly with the SCAS off and on. There was concern that the pilot could overload the aircraft with the SCAS off but control forces were considered light in both modes.
There was some discussion on whether or not the YC-15 should have a stick or yoke for control input. The intention was to have a “fighter-type” stick installed but there was some skepticism over it’s suitability from higher up the chain-of-command so the stick was removed. To counter, it was argued that the yoke obscured the view of the instrument panel.
The YC-15 had no natural warning upon entering the stall (i.e. vibration) so warning for the stall relied on an artificial “stick-shaker” to provide some warning within the critical angle of attack. This was judged as an inadequate solution because the shaker could activate in conditions of high thrust and flap settings when the aircraft clearly wasn’t in a stalling condition and because a high stink rate (such as during a STOL landing) could mask stalling conditions. As such, a Supplemental Stall Recognition System (SSRS) was developed and tested during the program. The SSRS provided an aural warning when the aircraft approached critical alpha during a given flight condition.
At gross weights of 149,300 the YC-15 flew STOL approaches at 87kts at a 6 degree glideslope giving a sink rate of 15.4 degrees per second. Conventional Takeoff and Landing (CTOL) approaches were normally made a 127 kts with a typical 8-12 feet per second sink rate with no flare at touch down. In STOL mode the aim-point for touch down was about 300 feet from the runway threshold . The YC-15 tested both flare and no-flare landing techniques in STOL mode. Testing at Edwards AFB showed the YC-15 was unable to land consistently in “hot-and-high” conditions in the required 2000 feet because of the slow actuation of the thrust reversers.
The thrust reversers could be used in-flight with some minor airframe buffet.
Testing the VAM, used approaches very similar to Navy carrier approaches were airspeed on approach is governed by angle of attack. The major issue was that the VAM didn’t display enough information to enable a completely “eyes-out-of-cockpit” approach.
33 STOL and CTOL off field demo landings, at Edwards, were conducted on 5000ft x 200ft runways with markers placed at 2000ft x 60ft. 5 pilots flew these tests and the YC-15s landing gear tire pressure was reduced. It was also found that the YC-15 could taxi over a 4-inch dump at 75-80kts. A unique procedures for the YC-15 during a STOL takeoff was extending the flaps from 14 to 23 degrees during the takeoff roll. Below is some archive video of STOL testing in 1975 (please pardon the music, Creed’s “Higher” just doesn’t work IMO):
During testing cracks were found in the blown flap material and fasteners had to replaced on a cracked rob. This was due to repeated exposure of hot jet exhaust. Direct Lift Control (DLC) (*see update below) was found to be effective for corrected high approach errors in the glide-slope but wasn’t effective for getting too low during approach. Flight path correction was done with a slightly high arrival at glideslope,correct with DLC, and then add thrust. Maximum DLC deflection angle was 20 degrees from flush on the upper surface of the wing. Orientation of the DLC actuation in the cockpit was a major “human factors” issue of debate among the pilots.
The YC-15 displayed docile engine out characteristics with mild crew indication 4-6 seconds after an engine out occurred. The YC-15 also was unable to meet the range requirement of 2600nm. The aircraft had more drag than predicted giving it a range of 1760nm.
I’ll be standing fast on this post for now. I’m splitting part 2 into this and an additional part detailing some of the operational and international demonstrations as well as technical improvements and further flight test results.
*[UPDATE]: For reader that may not know, direct lift control (DLC) is a system of spoilers, located on the upper surface of the wing. that either differentially control roll and in unison control pitch by dumping lift from the wings. They are common to most airliners.
I host a “Patch Tuesday” on my Facebook page. “Patch Tuesday” is my accumulated collection of various aviation patches I’ve collected through the years. I also occasionally share aircraft cutaways on the Facebook side. I decided that it’s time for something completely different.
I thought I’d try share some aircraft cutaways from my terabyte hard drive stash. Let me know what you think:
I’m going to start with the North American’s A-5 Vigilante:
The McDonnell Douglas YC-15 was a prototype developed of the USAF ‘s AMST program in 1972. The competition was the Boeing YC-14.
McDonnell Douglas developed the YC-15 from the Breguet 941s, using extensive wind tunnel testing (for optimum configuration testing) and using Cornell Aeronautical Labs B-26B In-Flight Simulator (for flight control testing).
The aircraft itself is 124.25 feet long, wingspan is 110.36ft, height is 43.30. Max gross weight is 216,680lbs. The interior cargo-box is 47 x 11.8 x 11.4.
Thrust for the YC-15 was provided by the JT8D turbofan (also the DC-9 powerplant) and produced a total thrust of 16,000lbs. The engines were mounted on shallow pylons mounted ahead of the wings leading edge. Thrust reversal was accomplished using so-called “daisy nozzles.” During final approach, with flaps fully extended and facing the engine, the engines provided 54% of the YC-15 lift.
The straight wings consisted of ailerons, double-slotted flaps, leading edge high lift devices (Kruger flaps, etc), and spoilers. The trailing edge devices, flaps and ailerons spanned 75% of the wings trailing edge. The flaps could extend as much as 46 degrees into the downstream. The YC-15 was the first jet powered aircraft to use externally blown flaps (EBF).
YC-15′s EBF
Flight controls consisted of the conventional hydraulic system and a stability and control augmentation system (SCAS). The SCAS was dual channel and 3 axis enabling hands off flight for high angle approaches (tactical approaches) and modes for attitude, altitude and heading.
The YC-15 saw the first use of a heads up display (HUD) system, specifically called the VAM (Visual Approach Monitor). Developed by Sundstrand, the VAM displayed the horizon, flight path scale, airspeed indexer and touchdown point.
Sundstrand’s VAM display
Being essentially a research airplane, the YC-15 did not need to fully conform to MILSPECS. As such it borrowed components from various aircraft, the DC-10 cockpit enclosure, the F-15 fuel pumps, the C-141 stabilizing struts, the A-10UARRSI, the C-5 cargo handling equipment and other parts from 9 other types of airplanes. Cockpit instrumentation used components from 10 different airplanes.
Here’s a cutaway of the YC-14 and YC-15 for comparison:
Part 2 will detail the YC-15s flight test program.
Part 3 will detail the YC-15 technological contributions to the C-17.
