Guy Norris/MILDENHALL
THE McDONNELL DOUGLAS (MDC) C-17 military transport has earned the nickname "The Moose" because of its impressive size and large, antler-like winglets. After years of doubt, it also seems to be earning the respect of crew and military administrators alike.
On 5 August, the US Air Force 437th Airlift Wing held a party at Charleston AFB, South Carolina. Tired C-17 crews and maintenance and support personnel celebrated the success of one of the most intensive service evaluations ever performed on a new USAF aircraft. Having achieved performance statistics better than most airlines, they had good reason for cheer. During the 30-day Reliability, Maintainability and Availability Evaluation (RM&AE), some 513 missions had been flown, of which 510 had run exactly to schedule - an on-time departure reliability rate of 99.2%.
"I can't remember when we gave a new weapons system such a thorough wringing out," says USAF vice chief of staff, Gen Thomas Moorman. "It is going to give the Army a lot more flexibility in the kinds of wars this country is going to have to fight, and the kind of places we are going to have to employ military force."
Make-or-break
The RM&AE was a critical make-or-break milestone for the C-17, which has struggled against a headwind of criticism. The exercise was a vital part of MDC's, and the USAF's, defence against the C-17's detractors who want to cap production of the airlifter at 40 aircraft. The Pentagon's Defense Acquisition Board is due to meet in November on the fate of the C-17, and the results of the mid-summer acid-test will be taken into account.
A look at the RM&AE scoreboard makes heart-warming reading for advocates of the C-17. One of the key parameters of the test was the amount of maintenance man-hours notched up per flying hour (MMH/FH). During the 30 days, the 12-strong fleet involved in the test achieved 2,252.5 flying hours and an impressive 4.2 MMH/FH against the USAF requirement of 28.4. Mean man hours to repair was only 2.5 against a requirement of 8.2.
Reliability was measured using four main parameters, the first of which was mean time between maintenance (corrective). This was fleet flying hours divided by the total number of removals of repairable line replaceable units (LRUs). The test achieved 1.5h, against the requirement of 0.62h. A second measurement was made of mean time between maintenance (inherent), or the flying hours divided by inherent maintenance actions. Again, the result of 3.1h was more than double the requirement of 1.29h. Mean time between removal, measured by dividing total fleet hours by the total number of removals of repairable LRUs, was 7.4h, against a target of 2.22h. The ultimate reliability measurement, that of successful missions actually completed, was 98%, against a USAF target of 85.7%.
Availability was measured by two main parameters: full-mission-capable and mission-capable rate. The first is the percentage of "clock-time" an aircraft is capable of performing all of its design missions. During the RM&AE, the C-17 achieved 85% against a target of 72.9%. The mission-capable rate is the percentage of clock-time an aircraft is capable of performing on any one of its assigned missions. In this category, the aircraft scored 91%, against a target of 80.7%.
Utilisation rates, measured in terms of fleet flying hours per aircraft per day, also exceeded target. The peacetime rate of 4.3h was achieved against a target of 3.2h, while the wartime sustained rate was 12.7h, against a minimum target of 10h. During two days of wartime "surge" flying, the tally was 16.6h on day one (against a 12.5h target), and a busy 17.1h on day two, against the same target.
Inevitably it was not all good news and the RM&AE showed up areas that still need improvement. One of these was the continuing problems with false alarms from the sophisticated built-in-test (BIT) system. Although the BIT correctly detected a malfunction 99% of the time against a requirement of 95%, the level of false indication was 61%, against a requirement of 5%.
Another, unrelated, incident occurred during the last few days of the exercise when a 0.76 x 2.44m composite panel detached from the underside of the wing of one aircraft and fell near the home of the commander of the 437th Airlift Wing. The composite fairing, part of the secondary structure, fell from the aft left-wing area just forward of the flap and between the two engines.
"We don't have a root cause yet, but bonding is suspect," says MDC, which has inspected the rest of the fleet and found nothing else like it. "We think it could have been a composite processing problem."
View from the flightdeck
Flight International experienced part of the RM&AE by flying with the 437th on strategic airlift missions from the USA to the UK and back. Col Kathy Conley, aircraft commander on "Moose 75" from Charleston and Dover AFB to RAF Mildenhall in the UK, says: "From a crew standpoint, the C-17 is working out really well. The two-crew cockpit is a big change from the older flightdecks that we're used to, like the C-141, and it does get busy during emergencies." Commenting on the use of the head-up-display, a first for a USAF transport aircraft, she says: "We can't figure out how we ever flew without it."
Some later improvements to the aircraft have been made as a direct result of USAF crew input. Lt Col Steve Stogsdill of the 17th Airlift Squadron and a member of the "Moose 96" crew which returned to Dover from Mildenhall towards the end of the RM&AE, is also part of the crew-operations resource team (CORT). The CORT meets regularly with MDC at Long Beach, California, to present problems which have turned up in operation and to help sort out solutions.
"We've seen some hardware and software changes as a result," says Stogsdill. "For example, the flap gauges were small and hard to read and did not indicate degrees. Some instruments, such as the air-refuelling annunciator light have been hard to read. As a result of our CORT meetings, we will be getting new ones."
Another planned improvement will come in the form of a new mission computer to replace the original Delco-made unit. "Right now, if we're putting in a complex mission, it takes a minute or two to crunch through. With the new one, it will be a matter of seconds. That will give us the ability to make instant decisions, which is sometimes what you need with a tight tactical situation."
Lockheed Martin Control Systems, which supplies the C-17's electronic flight-control system, is supplying the new Core Integrated Processor (CIP) under a contract potentially worth $35 million. Two units will be installed on each aircraft, replacing the three existing units. The first engineering development CIPs are scheduled for delivery to MDC in September, with prototype units following in mid-1996. Production is due to begin in the third quarter of 1997 for incorporation on aircraft P-41 onwards. The first 40 production aircraft will also be retrofitted.
Capt John Lipinski, commander of "Moose 96" and safety-investigation officer for the 437th, says: "We are totally amazed at what we can do with this aircraft." Lipinski, who flew the C-17 for several air-show demonstrations, including the 1995 Paris show, adds: "The C-130 and C-141 guys are amazed when you show them that you can take a 400kt [740km/h] jet carrying 80% of a [Lockheed] C-5 load, and put it down in less than 3,000ft [900m]. We as a force know what the aircraft can do, but others sometimes still need convincing."
Long Beach improvements
With a few weeks to go before the DAB's pivotal November decision, MDC is working intensely on changes and improvements to aircraft systems, structural design and manufacturing processes.
Aircraft P-33, the first Lot 8 aircraft, will be the first to benefit from a redesigned main undercarriage pod. This large unit, roughly the same overall size as an F-18, has been re-designed "from scratch" under a cost-saving initiative called design for manufacturing and assembly (DFMA). The new design removes 47%, or 16,621 fasteners, and 1,538 parts from the assembly. Recurring costs will be cut by 30% and the part will take ten fewer days (or 2,100h) to assemble, and 8,400h less time to install.
"We're starting to do that with other parts," says C-17 deputy programme manager, George Field. "By redesigning it like we did, we're making the parts themselves more efficient and cutting our capital costs at the same time." Other parts scheduled for DFMA treatment include the crew entry door and the overhead liners in the aircraft interior.
Other changes have resulted from inspections made to the structure of the durability test airframe which recently completed two lifetimes. "We found 92 'areas of interest', of which 41 were anomalies, or little cracks. Those of them that happened prior to the airframe passing through one-and-a-half lifetimes have been re-designed and incorporated on the line and retrofitted on the existing fleet. Out of the 41 most are so small that we won't need to do anything with them for a couple of years."
"We've also seen changes that will allow us to assemble it faster or that provide an overall improvement. For example, we've removed uneven paint [layers of] from parts of the wing, and removed aluminium-lithium from the cargo floor after we [MDC and the USAF] agreed that the weight saving of using the material didn't justify the cost of making it or the difficulties in working it."
A host of "affordability" changes are being looked at from Lot 8 onwards. These include design changes (such as the new pod), and new tooling and are mostly therefore not retrofittable. "They've really become our priority now that reliability issues are behind us," says Field. Affordability changes are the key to cutting the cost of each aircraft by up to 40% in the future, and a major weapon in the fight to extend production.
Savings of up to $1 million per aircraft are expected through a change to pre-coated fasteners from the previous labour-intensive method which required that each of almost 1.5 million fasteners be manually coated in sealant.
Further in the future, some more performance-enhancement changes are being studied. These include provision for windshear warning, a higher-performance braking system, and improved wet runway handling. A new lightweight engine nacelle design, offering savings in net aircraft weight of around 460kg, is also being evaluated for aircraft from around P-47 onwards.
The myriad cost-cutting initiatives, design improvements and the successful outcome of the RM&AE have spawned a new optimism at Long Beach. "A year ago, we were on probation, and now we're on the Dean's list," says Field. Now all that remains is to see if the enthusiasm of MDC and the USAF is matched by the Pentagon decision makers in November.
Source: Flight International
