Airtest – Canadair Challenger 601

Challenger History

When the late Bill Lear first introduced the Learstar 600 in July 1976, the aircraft was to be an extraordinary example of corporate aviation. For $4. 275 million you could purchase a third-generation business jet that could attain a high speed cruise of 88 match, a normal cruise of 85 games and a long-range cruise of  80 matches. Range at long-range cruise, with full IFR reserves, would be 4,000nm. The first flight was targeted for January 1978, certification was completed, first customer deliveries were to start by March 1979.

Construction work on the first prototype commenced in January 1977. By now the aircraft had undergone a number of changes; it was no longer the Learstar 600 but the Canadair Challenger model 600. The horizontal stabilizer had moved from a low position below the engine thrust line to a high T-tailed position. The aircraft had also gained a little weight and bulk. Negotiations had been held with both General Electric and Avco Lycoming – Canadair eventually deciding on the Lycoming ALF502 turbofan, a decision they would later regret.

Even at this early stage the Canadair salesmen had not been idle. At a time when first metal was being cut they had accumulated an astounding order backlog of 105 aircraft. Everybody it seemed wanted to own a Challenger. Amongst these 105 orders were 25 aircraft for the giant American courier company Federal Express. However, with the advent of deregulation, Federal Express were able to acquire and operate used Boeing 727s and McDonnell Douglas DC-10s and they subsequently cancelled the order for 25 freighters but did order one corporate version.

Canadair displayed a full scale mock-up of their aircraft at the 1977 NBAA Convention and the aircraft attracted considerable attention. The specifications were now frozen. From a construction and systems state-of-the-art standpoint, the 600 would be relatively straightforward. The design fatigue life would be 30,000 hours. The fuselage structure would be conventional semi-monocoque, of belt frames, stringers and chem-milled skins. The fuselage would be round to reduce the structure required for pressurisation to 9. 45psi, the total fuselage would be pressurised from pressure bulkhead to pressure bulkhead, including the underfloor areas. The cabin would have four standard evacuation openings – the forward door on the left side, two type Ill exits (one over each wing) and an aft external baggage door accessible from the cabin through the lavatory.

The wing would be based on four spars for damage tolerance and would be of a single structure with removable tip caps. It would be double swept with a sweep of 25 degrees at the 25% chord position. The aspect ratio would be 8. 5:1 with a wing loading of around 72 pounds per square foot.

The main landing gear comprised an articulating conventional air/oil strut and would be fitted with dual wheels and retract inwards. The nose gear would be a totally conventional unarticulated air/oil strut retracting inwards and also fitted with dual wheels. The gear would be hydraulically actuated, with hydraulically actuated downlocks for the mains and an over-centre brace for the nose gear.

Fuel would be carried in integral tanks between the front and rear spars. A pressure fuelling system would be standard and provision would be built into an area below the cabin aisle for additional fuel. This later became a necessity.

The performance figures caused some controversy. Canadair said the aircraft would depart a 5,000 foot runway at gross weight and go 4,000nm at . 80 mach with a 1,700lb payload. It was at this time that many people asked who will the Challenger would challenge most, the competition, or the Canadair engineers who must make the aircraft do what the salesmen had promised?

Serial number one rolled out of the Canadair factory on the 25th of May 1978 with a first flight scheduled for the end of July 1978. This would later slip to the 8th of November 1978. However, the Executive Vice President of Canadair, Harry Halton, the director of the Challenger programme would certainly hold his head high. He and his team of over 500 engineers, designers and draftsmen had brought an aircraft from a loosely drafted paper proposal to hardware reality and a marketing miracle in just 24 months. In fact, before the first prototype ever left the ground, the Challenger marketing team, headed by the well respected master marketeer – James B. Taylor, had accumulated over 130 orders. Canadair were still quoting their performance guarantees as:

• level flight speed of 505kts with a minus 20kts tolerance

• dry-tank theoretical range of 4,450nm with a minus 450 mile tolerance

• FAR 25 takeoff distance 4,700 feet with a plus 300ft tolerance

• FAR 25 landing distance of 4,600ft with a plus 300ft tolerance.

The price had now climbed to US$7. 25 million. This had made the owners of the first 50 aircraft a cool $3 million profit before even taking delivery of their aircraft; however, there was still some bad news to come. As the flight testing and certification programme got underway, it showed that the real life Challenger was going to be some 8,000lbs heavier than_the original design anticipated. Furthermore, the Avco Lycoming ALF502-L engines were proving to be at least 8% short on performance guarantees quoted by Lycoming. Lycoming would continue their tardy performance in being slow to deliver engines thus further delaying initial deliveries of aircraft.

With an increased weight and lower-than-expected engine performance the Challenger’s theoretical range had slumped from 4,000nm to just 2,875nm. The engineers were now working on increasing the aircraft’s gross weight to 40,350Ibs which included 1,500Ibs of fuel increasing the range to 3,200nm. The additional fuel would be stored beneath the floor and this would be a retrofit, at Canadair’s expense on the early deliveries. The undercarriage had already been designed to take the higher gross weight and only required minor beefing up.

The cruise speed also suffered. High-speed cruise was now . 80 mach, normal cruise . 75 mach and long range cruise was . 70 mach. However, the company was delighted to discover that the aircraft required significantly less runway than originally expected.

With all this dampening of enthusiasm, as regards the aircraft’s projected performance, the company was to suffer a further setback with the loss of prototype No. 1 during a deep stall accident. Prototype No. 2 took over the certification programme and after an additional 550 stalls to confirm that aircraft No. 2 had the same stall characteristics as No. 1, the data gleaned from prototype No. 1 was finally accepted and contributed towards the certification programme. Final FAA Certification was issued in November 1980 with several restrictions that would soon be lifted. By the time first deliveries began in April 1981 the price tag of a Canadair Challenger had climbed to $9 million or $9. 9 million with GE engines, with many people either opting or later wishing they had opted for the GE engines.

The Challenger 600 was now being marketed as a transcontinental aircraft and the Challenger 601 (which was in development and awaiting certification) was being marketed as the intercontinental jet.

The Lycoming saga finally came to a head in 1983 when Canadair had had enough and took out a $109 million lawsuit against Avco Lycoming alleging default in deliveries. The 600 was discontinued.

The Challenger 601

Canadair fell short of their projections with the 600 but the company put a major effort into the 601. To increase the range and performance they started with the 600’s aerodynamics.

The original wing structure had sufficient strength to enable Canadair to add winglets. Winglets made a lot of sense, they reduced the induced drag caused by wingtip vortices and increased the lift-drag ratio. The winglets were a relatively easy installation that did not significantly alter the aircraft’s stall characteristics and in fact improved the aileron effectiveness. Capt Boehm advised that with ttie winglets alone the 600 would ift 2,000lbs more, at least 2,000 feet higher at the same given temperatures and altitudes. This additional lift gave an immediate increase in range of about 140nm. To further enhance the range Canadair opted to increase the fuel load from 14,900Ibs to 16,665Ibs by making the optional underfloor tank of the 600 a standard installation on the 601.

The next step to increase the Challenger’s range took considerably more engineering. Canadair had now decided on the General Electric CF34-1A turbofan of 8,650Ibs thrust. In the GE engine, Canadair had a mature powerplant that had seen action on the Fairchild A-1O ground attack aircraft and the Lockheed S-3A Viking ASW aircraft. With all this military experience the powerplant was reliable but it still required civil certification which was consequently achieved in August 1982. Not only did the CF34-1A have 15% more thrust than the ALF 502L (8,650lb vs 7,500Ib) but its specific fuel consumption was also 16% better (GE 0. 36 vs LYC 0. 42). However, to install these heavier powerplants the engineers had to redesign and strengthen the rear fuselage area and the engine pylons and nacelles. The pneumatic starting system of the Lycoming was retained but the integrated drive for the 30 Kva generators had to be altered due to the different running speeds of the CF34.

With these changes Canadair had produced an intercontinental jet which had a range with full IFR reserves of 3,400nm. A high speed cruise of . 80 mach, normal cruise of . 77 mach and long-range cruise of . 74 mach. The balanced field length at gross weight remains a very respectable 5,350ft at sea leve an ISA day. Landing distance at maximum landing weight, Is a mere 3,550ft again at sea level in ISA conditions.

Systems

The Challenger is certified to the latest FAR Part 25 design criteria and as such, has had to endure an extremely rigorous certification programme. Reliability and longevity are just two of the by-products of such a rigorous process. The Challenger has two totally independent sets of flight controls, so should one system be jammed, by simply deploying a manual disconnect, the aircraft can return to base on the remaining system. It has three completely independent hydraulic systems, with two separate power sources, allowing for complete aerodynamic control of the aircraft even with both engines failed.

Hydraulics power the Challenger’s flight control system, landing gear, brakes and nosewheel steering. The Challenger’s control surfaces are like a high speed fighter, employing irreversible hydraulic actuators. The pilot has no direct feedback to judge the control load, nor does he require this as control feel is induced artificially by means of springs.

The 3000psi hydraulic systems consist of three parallel, continuously operating, power circuits. Each functions independently of the other; there are no provisions for exchange of hydraulic fluid or power between the three systems. As mentioned earlier, even the flight controls are split. The left aileron, left elevator and right spoileron are powered by the No. 1 hydraulic system. The right aileron, right elevator and left spoileron are powered by the No. 2 system. Each system contains two hydraulic pumps. System No. 1 receives its hydraulic pressure for all flight modes from a pump on the left engine, but an AC motor-driven pump is manually engaged to back up the engine-driven pump during takeoff and landing. System No. 2 is similar except that its primary power comes from the right-hand engine.

The third system employs two AC motor driven hydraulic pumps, with one pump operating continuously in all flight modes and the other being manually engaged during takeoff and landing, or in the event of failure of the third system’s first AC pump. The Challenger’s air driven generator (more of which later) supplies electrical power to one of the system’s three hydraulic pumps in the event of a dual engine failure.

Whilst the Challenger is dependent upon hydraulic power, the systems redundancy would ensure very little or no increase in pilot workload should a problem develop in the engine driven systems.

The Canadair Challenger is the first business aircraft to employ an all-AC electrical power system. It is made up of four separate sources starting with two Sunstrand integrated drive generators. These two 30 Kva units produce constant frequency, three-phase 400 Hz, 115/120 volt AC, at all engine operating speeds.

A third 30 Kva generator is driven by an Air Research GTCP 36-100E APU, but unlike the engine driven units this one does not require the constant speed feature since its required speeds are maintained by the APU’s governor. A fourth AC source, capable ol producing 30 KVa of three phase, 400 Hz, 115/120 volt AC can be brought on line by deploying an air driven generator. The air driven generator is used for emergency power when all other units are inoperative or when the APU is required but cannot be used (the APU must be off by 30,000ft). The air driven generator automatically senses when it is needed and deploys itself within four seconds. Should it fail to respond to the automatic signal it can be released manually. Once in the airstream, the unit is capable of powering all essential aircraft loads.

Secondary DC power, for starting the APU and required for some avionics, aircraft sensors and instruments that must be operational before the APU’s generator comes on line, is supplied by a nicad storage battery. Once the AC generators are on line AC is converted to DC by static invertors.

The pneumatic system is used for air conditioning/ pressurisation, wing and engine anti-ice, crew foot warming and windshield demisting, engine starting and thrust reverser deployment. The pneumatics are tapped off the 10th and 14th stage bleed air sources on the engines. However, for engine starting the pneumatics are taken from the APU or an external ground source.

There are two separate air conditioning units that provide temperature-controlled air from the pneumatic system, either of which can independently supply the entire aircraft. The foot warmer and windshield demist system operates independently from the two air conditioning units and can be employed as an emergency pressurisation system should both air conditioning units fail. By the way, the cabin differential can operate up to 9. 1psi giving an 8,000ft cabin at a cruise altitude of 41,000ft.

Flying the Challenger

The most significant thing one notes when reaching the top of the airstair is the enormous passenger cabin. With a maximum width of 8. 16ft this flat floored environment offers considerable flexibility in internal arrangements that can seat from 8 to 30 passengers. I found all the options and layouts shown to me to be very appealing but there is obviously endless scope for any chief executive to personalise his Canadair Challenger.

From the pilot’s viewpoint, the Challenger 601’s flight deck offers everything. All the very latest in avionics and navigation systems, ample room to spread out and absolutely superb visibility. There is a broad centre console that contains the almost mandatory dual or triple navigation systems, avionics and auto pilot controls. Absolutely eveything is easily accessible and falls into an easy scan pattern.

Apparently the Challenger 600 was a little touchy in the nose wheel steering, but I found absolutely no evidence of this at all in the 601. The Canadair’s engineers have developed a very smooth ·steer by wire’ system that is a delight to use. We taxied out with both engines running but one reverse thrust bucket was deployed to control forward speed and avoid excessive heat build up in the brakes.

During the taxying phase out to Sydney’s runway 16, I had not taken much note of the noise levels, but imagine my amazement when I applied takeoff power and accelerated down the runway in virtual silence. Had I not climbed aboard this aircraft and taken off myself, I might just as easily have been in a simulator.

The unstick forces were very predictable and comfortably light.

Initial climb out at 8° nose up gave excellent visibility and the CF34’s accelerated the aircraft smoothly and positively to 250 KIAS climb speed. Both the lateral and longitudinal stability of the 601 is excellent making the aircraft a sheer delight to hand fly. Because of the excellent handling qualities· speed stability is exceptional and it is very easy to nail either a climb or an approach speed and maintain it, precision flying is made easy in the 601.

The ailerons gave excellent response and I believe one can achieve a roll rate of 80° per second which is very brisk for an aircraft of the Challenger’s size. I set the aircraft up in an approach mode with gear and flaps down, once the aircraft was trimmed and sufficient power applied, I let go the controls and the aircraft remained stable and simply flew itself. It was still difficult to accustom myself to the eerie sensation of ghosting around the sky in total silence and not even experiencing any wind noise. The cabin would be a very pleasant environment indeed on those long trans-Pacific flights for the CEO.

All too soon it was time to return to Sydney. The inital descent was at 340 KIAS which we were able to hold until approaching the coast. Spoiler deployment offered no surprises, pitch and roll reponses remained normal and the speed washed off quite rapidly. We joined the runway 16 ILS at 7DME and the aircraft’s inherent stability allowed a precise intercept of the glideslope which was not too difficult to maintain. The articulating undercarriage provided a smooth touchdown, which probably surprised me more than Captain Boehm. The deployment of reverse thrust had us decelerating rapidly to taxi speed. On the taxi back to the Qantas Jet base we shut one engine down which offered smoother speed control, as the engines do have considerable residual thrust.

The Canadair Challenger 601 is a superb example of state of the art business jet technology. The aircraft enjoys excellent support from the manufacturer and this was substantiated and emphasized by numerous Challenger operators who were _canvassed on the subject.

The aircraft may not be quite what Bill Lear envisaged in 1976, but then it is pretty close. It now has true intercontinental range with the flexibility of a 5,300ft balanced field length and offers an opulent, comfortable cabin environment. Yes, the Challenger 601 has earned and deserves its postilion amongst the big three in the corporate heavy iron stakes. Additionally, by the time this article goes to press, we can look forward to seeing a Challenger 601 grace our skies on a permanent basis.

Should any potential purchasers require more information on the 601, I am sure that Mr Ron Walker of Jet Direct Pty Ltd, the Australian Agent, would be pleased to oblige.