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The Lockheed-Aermacchi T-Bird II is powered by a 4,000-pound-thrust Rolls-Royce Viper turbojet that gives it excellent performance at altitude and provides quick throttle response in the landing pattern.
This is the third in a series of reports on the aircraft expected to compete for the U.S. Air Force-U.S. Navy Joint Primary Aircraft Training System (JPATS).
The Lockheed-Aermacchi MB-339A T-Bird II turbojet trainer is a strongly built, simple aircraft that handles well throughout a wide performance range.
The T-Bird II (from the nickname for Lockheed’s original two-seat T-33 Shooting Star) is powered by a Rolls-Royce Viper RB582-01, a 4,000-pound-thrust de-rated version of the 4,450-pound-thrust Mk. 68043 engine in the Royal New Zealand Air Force’s new MB-339CB trainers. The engine, fitted with a straight hydromechanical fuel control, is scheduled for 4,500 hours between overhauls. Versions of the aircraft are in service in Italy, Argentina, Peru, Malaysia, Nigeria, Ghana, Dubai, and New Zealand.
Although JPATS competitors are not required to land aboard ship, initial requirements specified that the aircraft must be capable of maintaining optimum angle-of-attack from downwind leg to final in all landing configurations—obviously a Navy input. Interestingly, Naval Air Training Command instructors were able to fly constant angle-of-attack approaches to touchdown using the mirror when the T-Bird II toured training command bases. Sink rates at normal approach speeds, no-wind on a 3° glide slope are 10.4 feet per second, and the aircraft is stressed for 12 feet per second. That does not leave much margin for error, but it does offer some potential training advantages.
Conservatively, instructors could introduce primary students to field carrier landings under controlled conditions. The aircraft is designed for a 30,000-hour structural life, well in excess of the tentative operational requirement of 18,240 hours (65 hours per month over 24 years). Still, training advantage would have to be balanced against longterm maintenance requirements.
The flight controls are mechanical, linked by pushrods and bellcranks; the ailerons have hydraulic servos but the aircraft can be flown without them. The 2,400 pounds-per-square-inch normal hydraulic system powers the nose wheel steering, flaps, landing gear, normal brakes, speed brakes, and the aileron servos. An emergency system lowers the gear and powers the wheel brakes.
The aircraft has two generators, either of which can carry the entire alternating current load, and two batteries—linked in series for starts but paralleled in the event of generator failure, when they can provide 1.5 hours of electrical power.
n n n
34.8 (1 (11.220 m>
8.1 It
(2.483 m )
Performance | |
Takeoff distance over 50-foot obstacle (sea level) | 2,750 feet |
Time to climb to 25,000 feet | 6.5 minutes |
Rate of climb @ 25,000 feet | 2,6000 feet/minute |
Sustained load factor @ 25,000 feet | 2.8 g |
Maximum level speed (sea level) | 475 knots |
Approach speed | 98 knots |
Landing distance (50-foot obstacle) | 2,470 feet |
( 3.994 m )
13.1 ft
The T-Bird II sits low to the ground and provides excellent visibility over the nose; the front-seater is practically sitting on the taxi stripe and forward hemisphere visibility from the stepped-up rear cockpit is even better. All doors and panels are easily accessible for preflight and turnaround inspections, and all have pushbutton latches.
I flew the aircraft with Lockheed experimental test pilot Kenny Grubbs, from the Lockheed facility at Dobbins Air Force Base, Marietta, Georgia. The demonstrator has Martin-Baker Mk-lOF zero altitude-zero airspeed ejection seats with the normal number of straps and leg restraints—a great harness for inverted spins, as I later verified. The seats eject through the canopy, which reduces sequencing complications, and a command-select option is available in the rear cockpit.
I took the front seat to get a student’s perspective. Starting the aircraft is simple—and you move the throttle to idle before hitting the start button. The start sequence: throttle to idle, batteries on, engine master on, hit the start button, and watch the engine light off and accelerate to idle—40%. Post-start checks are standard—cycling flaps, speed brakes, and trim before selecting takeoff settings. Nose-wheel steering is selectable with a standard stick-mounted button: click on and it remains engaged until clicked off. A glare shield-mounted advisory light indicates status.
fitted under the wings can provide another 1,080 pounds, which makes the maximum total fuel load 4,040 pounds.
The demonstrator aircraft’s empty weight is 7,050 pounds; the aircraft weight at start for our flight was close to 10,100 pounds, which included 2,550 pounds of fuel—1,300 pounds in the fuselage and 625 pounds each in the wingtip tanks.
We taxied out just after an early-De- cember cold front had passed through, leaving in its wake clear skies, 43° temperatures, and winds from 340° at 14 knots gusting to 24—a 50° right crosswind for Runway 29 at Dobbins that gave us a resultant of about 19 knots at 90° in the gusts.
Cleared for takeoff, I took the centerline, pushed the power up to 100%, checked the gauges, wiped out the cockpit, and rolled. Trainers must be forgiving—on the ground and in the air—and the MB-339A showed only a slight tendency to weather-cock into the wind on takeoff roll; there was no tendency for the upwind wing to lift as the low-slung T-Bird II approached lift-off.
I had the nose-wheel steering engaged for the initial portion of the roll but the rudder became effective quickly and I clicked it off.
Normal takeoff speed is 100
I
I
knots but we added 10 knots to give us a margin in the gusts. The gear and flap handles are conveniently located and the aircraft accelerated smoothly as I crabbed right to stay on runway heading for climb out. We were airborne in just under 1,600 feet.
The rate of climb was 6,000 feet-per- minute passing 5,000 feet, and 4,800 feet- per-minute climbing through 10,000 feet. The canopy rails are low and visibility is excellent. Clear of the many airways that converge on Atlanta, we leveled off at 12,000 feet so I could get some feel for the aircraft. The aircraft responded well as I did some hard turns, aileron rolls, and wingovers prior to setting up for a series of overhead maneuvers. The aircraft rolls at 180° per second at 270 knots, Grubbs told me.
Of course, the solid feel was partly because we were at a relatively low altitude, staying below area positive control. Air space throughout the United States is at a premium, and the services are emphasizing JPATS performance at altitude (20,000 to 25,000 feet).
There is little room to expand laterally, but there is still some room at the top in already-designated air space. This range is well within the MB- 339’s envelope but the real test will come during the formal evaluations that will begin later this year (see sidebar). Testing will include formation flight and the aircraft will be required to demonstrate satisfactory power reserves during breakup and rendezvous training.
“The aircraft will do squirrel cages all day long at 20,000 feet using 100%,” Grubbs said. He added that he had done loops at 30,000 feet, “. . .but that puts you over the top at about 60 knots.”
It is at altitude that the jets would seem to enjoy their biggest operational advantage over the turboprops in the competition, although the turboprop contenders have beefed up their power plants to improve high-altitude performance. In addition, good high-altitude performance can translate into more training opportunities on dual flights if the tops are not too high.
“We’ve done a significant amount of engine work with Rolls-Royce and the aircraft’s capability at altitude is our real advantage,” L. Gary Riley, Lockheed vice-president and JPATS program manager, said.
We set up for a standard 4g loop— using 92%—at 270 knots at 11,000 feet and topped out at 14,300 feet indicating 130 knots. I had the aircraft nibbling on the buffet and it was easy to pick up the angle-of-attack indicator near the top of the instrument panel for a cross check.
After a series of one-half Cuban Eights, I leveled off at 17.000 feet and stalled the aircraft power-off. There was plenty of warning buffet and the aircraft stalled straight ahead at 100 knots without any tendency for a wing to drop. The ailerons remained effective as I lowered the nose slightly and added power; the aircraft actually climbed out of the stall in this configuration. Stalling the aircraft wings- level with gear-and-flaps down produced the same results as the stall came at 92 knots. Still in the landing configuration, I rolled into 25° angle of bank and pulled the aircraft into an approach-turn stall. At the break, I added power and leveled the wings and the aircraft recovered immediately with little loss of altitude. Once again, the ailerons remained effective throughout the maneuver with little tendency toward adverse yaw.
Spin entry at 17,000 feet was standard: power to idle, raise the nose 20° above the horizon, feed in full rudder and full back stick at the stall—and hold what you’ve got. The aircraft pitched over, and stabilized at about 60° nose down. We did four turns to the left, losing about 600 feet per turn, and I stopped the spin using opposite rudder and neutral stick. Then, with the controls neutral, I eased on the g, added power as the nose came up through the horizon, and we were back at 17,000 feet in about a minute. This time I went right and, after four turns, let go of everything—the aircraft stopped rotating, tucked, and stabilized about 70° nose down. All I had to do was pop the speed brakes and recover using optimum angle-of-attack.
Back at 17,000 feet, I tightened my harness and Grubbs talked me through an inverted spin; nose up, roll inverted, full left rudder, and put the stick in the forward right-hand comer of the cockpit— full forward stick and full right aileron to start the roll; the aircraft is quite spin resistant when inverted, he said. As the Georgia countryside began to rotate. I did remember to check the angle-of-attack— which was down around zero. Entering the second turn, Grubbs slammed the throttle from idle to 100% and back several times with no noticeable effect on the engine.
I had been counting the turns. As we finished number four I went to neutral stick and opposite rudder and the aircraft stopped rotating almost immediately. Re-
key—1,500 feet AGL downwind abeam touchdown—slowing to 120 knots and selecting half flaps. Even so, I was wide and ended up angling. I dropped full flaps when we had the field made, touched | down long, and entered the touch-and-go pattern.
Downwind at 1,500 feet AGL, I picked up optimum angle-of-attack, which corresponded to 115 knots af our gross weight. I was consistently high at the 90° |
position—and angling—on four full-flap |
approaches and the ball came off the top of the mirror, but a high dip usually got it somewhere near the center on final. Again, because of the gusts, I flared with a little power on touchdown.
We shot two no-flap landings—140 knots downwind, 125 on final, touchdown at 110. The aircraft is clean and, with | its straight wing, floats a long way. I i found no tendency for the low-slung aircraft’s wing to lift on roll out in the gusty I conditions regardless of flap position. Mastin said he would like to see the fly- off conducted at Reese Air Force Base, Lubbock, Texas. Reese, 3,340 feet above sea level, has a 6,500-foot runway, and , often experiences high temperatures and winds; the Air Training Command cancels 8%-10% of its T-37B sorties at Reese—and at Vance AFB, Enid, Oklahoma—because of crosswinds that exceed the T-37’s 17-knot limit, according to the operational requirements document.
The MB-339 has a 25-knot limit.
We pulled into the chocks and shut down with 700 pounds of fuel remaining; we had burned 1,850 pounds of fuel on a 1.3-hour flight that included 25 minutes in the landing pattern.
JPATS Update
After delays caused by Defense Department meddling and a change of administration, the JPATS program office released the draft request for proposals (RFP) on 1 February 1993. The formal RFP is scheduled to be issued on 1 September with responses due 1 November. Flyoffs will follow and contract award is scheduled for June 1994.
The ground-based training system (GBTS) requirement now will be competed separately later, a major change in that GBTS suppliers had previously been required to team with aircraft contractors.
The Joint Chiefs of Staff roles-and-missions study is
sued in mid-February does not appear to affect the JPATS competition. The study does recommend the consolidation of Navy, Marine Corps, Coast Guard, and Air Force initial fixed-wing training in “ ... a common primary aircraft,” which would be the JPATS winner, and states that “ ... by the end of 1994, the Navy and Air Force will have developed joint primary training squadrons at two locations.” Also, Navy, Marine Corps, and Coast Guard helicopter training could be moved from Pensacola, Florida, to Fort Rucker, Alabama, “ ... if it proves cost effective.”
covery after that was by the book. But there was more to come, as Ken then demonstrated a lomcovak entered from the pure vertical—complete with some more throttle slams; again, not a murmur from the engine.
“We’ve put the [installed] engine through tests it would never see in ser-
LOCKHEED
Rear-seat instructor-eye view on short final.
vice use,” Brian Fortune, Rolls-Royce senior flight test engineer, told me. The turbojet Viper has excellent acceleration characteristics; ground idle (40%) to full military in 4.5 seconds; in flight (60%) to full military in 3.5 seconds; and approach power (80%) to full military in 1.5 seconds. This last figure has particular significance in the landing pattern.
The Lockheed-Aermacchi-Rolls Royce team believes that the engine—the lone turbojet in the competition to date—gives them an edge despite higher fuel consumption than the turboprops and turbofans in the other contenders. “Fuel costs are a very small fraction of life-cycle costs . . . training value per dollar is a much better measure, and I doubt that anyone, even the turboprops, will beat us there,” Joseph H. Mastin, Lockheed’s JPATS requirements manager said.
On the way back to Dobbins, we accelerated to 450 knots and checked the aircraft’s high-speed handling capabilities, which felt good to me.
The high winds at Dobbins cost us what would have been a first for me: shutting down a single-engine aircraft in flight—on purpose. Lockheed emphasizes the T-Bird II’s systems independence and Grubbs told me that he regularly shuts down the engine on demonstration flights. “We’ve got 1.5 hours of battery power and the flight controls work fine without the aileron hydraulic servos,” he said. But, while there have been no difficulties with air starts and the essentially straightwing aircraft (with a 14:1 glide ratio) should be capable of a flameout approach in the hands of a proficient pilot, under the circumstances it was hardly prudent to complicate matters.
The aircraft’s 150-knot maximum- range glide speed coincides with the best air-start speed. Typical engine failure procedures for single-engine jets specify a minimum airspeed/altitude combination for attempting an air start—absent those conditions, ejection is normally the only option. Given enough altitude to try though, “ ... the last thing a student [with an engine failure] needs to worry about if he’s got problems is extending a ram air turbine to get back electrical or hydraulic power,” Grubbs said.
I settled for a simulated flameout approach back at Dobbins: 150 knots with the power at idle and the speed brakes half out. I dropped the gear at high key— 2,500 feet above ground level (AGL), on runway heading, over the intended point of touchdown (halfway down the runway); compensating for the wind, I turned more steeply than normal toward low
Lieutenant Colonel Greeley is an associate editor at Proceedings. He flew A-4s throughout his career, which included service in Vietnam and duty as operations officer of an advanced jet training squadron flying TA-4Js. He commanded VMA-223, an A-4M squadron, prior to his retirement in 1982.