ATP's - Never mind payload, it's reliability you need to worry about
Regarding ATP reliability, the following should just about cover it.
Undaunted by technical realities, the design team at British Aerospace has announced plans for the ATP-XL, promising more noise, reduced payload, a lower cruise speed, and increased pilot workload.
We spoke to Fred, a former British Rail boilermaker, and now Chief Project Engineer. Fred was responsible for developing many original and creative design flaws in the service of his former employer,
and will be incorporating these in the new ATP-XL technology under a licensing agreement. Fred reassured ATP pilots, however, that all fundamental design flaws of the original model had been retained. Further good news is that the XL version is available as a retrofit.
Among the new measures is that of locking the ailerons in the central position, following airborne and simulator tests which showed that whilst pilots of average strength were able to achieve up to 30 degrees of control wheel deflection, this produced no appreciable variation in the net flight path of the aircraft. Thus the removal of costly and unnecessary linkages has been possible, and the rudder has been nominated as the primary directional control.
In keeping with this new philosophy, but to retain commonality for crews transitioning to the XL, additional resistance to foot pressure has been built in to the rudder bias system to prevent over-controlling in gusty conditions (defined as those in which wind velocity exceeds 3 knots).
An outstanding feature of ATP technology has always been the adaptation of the PW100 engine, which mounted in any other aircraft in the free world is known for its low vibration levels. The ATP adaptations cause it to shake and batter the airframe, gradually crystallising the main spar, lock the port maingear after retraction, desynchronise the accompanying engine, and simulate the sound of fifty skeletons fornicating in an aluminium dustbin. BAe will not disclose the technology they applied in preserving this effect in the XL but Fred assures us it will be perpetrated in later models and sees it as a strong selling point. "After all, the Concorde makes a lot of noise" he said, "and look how fast that goes."
However design documents clandestinely recovered from the BAe shredder have solved a question that has puzzled aerodynamicists and pilots for many years... how does the ATP actually fly ?? These documents disclose that it is actually noise which causes the ATP to fly - the vibration set up by the engines, and amplified by the airframe, in turn causes the air molecules above the wing to oscillate at atomic frequency, reducing their density and creating lift. This can be demonstrated by sudden closure of the throttles, which causes the aircraft to fall from the sky. As a result, lift is proportional to noise, rather than speed.
Fred was at pains to point out that during the take-off phase, the previous equation is not applicable as the net take-off flight path is completely proportional to the willpower of the flightdeck, cabin crew and passengers combined. "Any single person not willing the aircraft to become airborne could cause a major accident," he commented.
In the driver's cab (as Fred describes it) ergonomic measures will ensure that long-term ATP pilots' deafness does not cause in-flight dozing. Orthopaedic surgeons have designed a cockpit layout and seat to maximise backache, en-route insomnia, chronic irritability and terminal (post-flight) lethargy. Redesigned "bullworker" elastic aileron cables, now disconnected from the control surfaces, increase pilot workload and fitness. Special noise retention cabin lining is an innovation on the XL, and it is hoped in later models to develop cabin noise to a level which will enable pilots to relate ear-pain directly to engine power, eliminating the need for engine instruments altogether.
We were offered an opportunity to fly the XL at British Aerospace's development facility, adjacent to the BritRail tearooms at Little Chortling. (The flight was originally to have been conducted at the Prestwick plant but aircraft of BAe design are now prohibited from operating in Scottish airspace during avalanche season). For our mission profile, the XL was loaded with Benbecula passengers for a standard 100 nm trip with BritRail reserves, carrying three pilots (all Captains, due to crew shortages) and 68+40 passengers (all from the same family) to maximise discomfort.
Passenger loading is unchanged, the normal 'prop rotating in wind of 5 knots, due to slack groundstaff failing to secure it' syndrome, inflicting serious lacerations on 71% of boarding passengers, and there was the usual confusion in selecting a seat appropriate to the nearest emergency exit. The facility for the clothing of embarking passengers to remove oil slicks from engine cowls during loading has been thoughtfully retained.
Start-up is standard, and taxiing, as in the standard ATP is accomplished by brute force. Takeoff calculations called for a 250-decibel power setting, and the rotation force for the (neutral) C of G was calculated at 180 ft/lbs. of backpressure.
Initial warning of an engine failure during takeoff is provided by a reduction in vibration of the flight instrument panel. Complete seizure of one engine is indicated by the momentary illusion that the engines have suddenly and inexplicably become synchronised. Otherwise, identification of the failed engine is achieved by comparing the vibration levels of the windows on either side of the cabin. (Relative passenger pallor has been found to be an unreliable guide on many ATP routes because of ethnic consideration).
Shortly after takeoff the XL's chief test pilot, Capt. Bloggs, demonstrated the extent to whch modern aeronautical design has left the ATP untouched; he simulated pilot incapacitation by slumping forward onto the control column, simultaneously applying full right rudder and bleeding from the ears.
Whilst initially noting nothing out of the ordinary, on discovery that Capt. Bloggs actually was incapacitated, the crew of the XL discovered that, like its predecessor, it demonstrated total control rigidity and continued undisturbed. Power was then reduced to 249 decibels for cruise, and we carried out some comparisons of actual flight performance with graph predictions. At 5000 ft and ISA, we achieved a vibration amplitude of 500 CPS and 240 decibels, for a fuel flow of 700kgs/hr making the ATP-XL the most efficient converter of fuel to noise after the Titan rocket.
Exploring the Constant noise/Variable noise concepts, we found that in a VNE dive, vibration reached its design maximum at 1000 CPS, at which point the limiting factor is the emulsification of human tissue. The catatonic condition of long-term ATP pilots is attributed to this syndrome, which commences in the cerebral cortex and spreads outwards. We asked Capt. Bloggs what he considered the outstanding features of the XL. He cupped his hand behind his ear and shouted "Whazzat?"
We returned to British Aerospace, convinced that the XL model retains the marque's most memorable features, whilst showing some significant and worthwhile regressions.
BAe are not, however, resting on their laurels. Plans are already advanced for the HS748-XL and noise tunnel testing has commenced. The basis of preliminary design and performance specifications is that lift increases as the square of the noise, and as the principle of acoustic lift is further developed, a later five-engined vertical take-off model is also a possibility.