ATR: Top of the props

 It was August when the very first example of the ATR 72-600 was delivered to Royal Air Maroc at its Casablanca base. Early indications are impressive with the aircraft achieving a perfect technical despatch reliability of 100% over its first six weeks of service.

This may come as no surprise to the other 175 ATR operators, in 94 countries spread across all five continents, where the despatch reliability for the whole ATR fleet (with 845 aircraft presently in service) equals 99.6% and marks out the company as the world’s No1 turboprop manufacturer.

The first delivery of the ATR 42 (48-50 seats) was in 1985, followed by the first ATR 72 (68-74 seats) in 1989. This latest -600 series represents another step by ATR along a highly focused and predetermined path of significant product improvement.

Building on the success of the -500 (engines, advanced six-bladed propeller, vibration damping and high levels of passive cabin noise suppression, etc), the -600 introduces a completely new, fully digital flight deck, supporting all the latest civilian aviation avionic requirements and featuring a five-screen, full ‘glass cockpit’ layout supplemented by (as an option) two, large, Class 2 electronic flight bags (EFB), one for each pilot.

This new flight deck is now married to a re-modelled, ultra modern and luxurious cabin – named the ‘Armonia Cabin’ – designed by the Italian company Giugiaro Design. Other cabin options include an in-flight entertainment system, a dual-class cabin (with three abreast wider business class seats forward and with the new prestige or classic seats four abreast to the rear), a forward passenger entry door and jet-bridge docking capability.

ATR has already taken more than 220 orders for the -600, including 130 firm orders in 2011 alone. The current order backlog stands at more than 270 aircraft and the company plans to ramp up production to 72 aircraft per year (or more) from 2012 onwards, at which stage all ATR 42/72 will be produced to the -600 specification.

The present order breakdown per type is approximately 10% for the ATR 42 and 90% for the ATR 72. Both types (and also at present both the -500 and the -600 series) are assembled on the same production line at Toulouse. The ATR 42/72 have 90% commonality of parts, including the engines (PW127M), which are ‘chipped’ electronically to suit the individual power requirements of the ATR42 or the ATR72 and then with options for power increases to suit very short field or hot/high operations.

ATR is a 50/50 partnership between EADS and Finmeccanica. EADS produces the wing with Finmeccanica delivering the complete fuselage and fin/tail. Pratt and Whitney delivers the engines and Ratier (a division of Hamilton Standard) delivers the highly swept, six-bladed, 3.93m diameter propeller (incidentally, Ratier also deliver the advanced propellers for the Airbus A400M).

Composites in the ATR 42/72 -600 make up around 20% of the airframe, primarily used in all of the tail structure and large sections of the front and rear wing structure. Large parts of the airframe are designed and standardised using the CATIA system, ensuring that the delivered parts fit perfectly on the production line without any need for rework. The Toulouse ATR production line sits alongside that of Airbus and the link through EADS to Airbus engineering allows ATR to directly utilise state-of-the-art aerospace technology, as employed on the latest Airbus A380. This now grants the -600 series a level of technical and avionic sophistication not seen before on a regional aircraft or among its closest competitors.

 

 

Economics

 

The regional air transport aviation world in 2011 is now a very different place from the same industry as seen in 2000. Then, the reasonably low cost of oil and a new generation of small, more fuel efficient, jet engines allowed new regional jets to predominate and threatened to make regional turboprops extinct, with Saab, Fokker, Dornier and BAe Jetstream all going bankrupt as aircraft manufacturers. However, the inexorably rise in oil prices and the fact that all international agencies agree that the price will only continue to increase over the next 20 years, means that a new generation of advanced regional turboprop airliners, that the ATR -600 series now represents, is already back on track to recapture their former market place.

On a typical 250nm sector length, flight times are almost identical regardless of an aircraft’s ultimate top speed but a regional turboprop will always remain unbeatable in terms of economics, to such an extent that it can reduce an airline’s direct operating costs by up to 45%, when compared to a similar size regional jet airliner. To put this into some form of perspective, if an airline was equipped with a 20-strong regional turboprop fleet it could save itself in excess of $33 million on annual fuel costs alone (at May 2011 fuel prices) when compared to a similar fleet of 20 regional jets and when flown at the same typical levels of annual utilisation. In addition to rising fuel costs are the massive potential extra costs of complying with future carbon emissions trading schemes, starting in Europe in 2012. The turboprop will again save money by producing several tons less CO2 per flight hour.

ATR is quoting a purchase price of around $18 million for an ATR42-600 and around $22 million for an ATR72-600; prices that it states are considerably cheaper than its nearest competitor.

ATR forecasts that airlines will need more than 3,100 new turboprops in the period 2011-2030 and this is predicted to generate a market for manufacturers valued at $73.5 billion. Around 70% of that total (2,100 units) is represented by 50-70 seat turboprop types and ATR sees great potential for its aircraft in the emerging markets of Latin America, Africa/Middle East and Asia/Pacific.

The company presently has more than 60% of the 50-70 seat turboprop market but the ATR -600 series now represents its determination to build on that with an aircraft that can leapfrog both its jet and turboprop competitors and with a product that both ‘technically’ for its crew and ‘look and feel’ for its passengers, far exceeds present industry perceptions.

 

First impressions

 

My evaluation flight took place in early September from Toulouse-Blagnac (LFBO) using ATR42-600 registered F-WWLY. The aircraft was at production standard (so it can be converted and sold as a production unit a later date), but retained a test instrumentation equipped cabin and a small amount of additional cockpit test instrumentation for on-going avionic development by the flight test department.

On entering the cabin, it was gratifying to see that no part of the wing spar impinged into the upper cabin roof and no part of the main gear impinged into the lower cabin walls, so the cabin itself was a perfectly uniform tube. The large, numerous and closely spaced cabin windows let in a tremendous amount of natural light.

After the flight I was shown the full production Armonia Cabin by ATR head of communications, Sonia Dumas. With new lighting, new seats, remodelled and larger overhead bins, an internal cabin width of 2.57m, an aisle width of 0.47m and an internal cabin height of 1.91m from a flat floor, the overall effect was nothing short of visually stunning and beautifully modern. I believe passengers in the ATR-600 will have the feeling that they are travelling in a 21^st century aerospace ‘air vehicle’ but where the aircraft’s type of propulsion is now virtually immaterial.

On entering the cockpit I was immediately struck by how roomy, ultra modern and uncluttered it looked and how Airbus-like it felt, including the overhead panel, and with all switches adhering to the ‘dark cockpit’ philosophy. The Thales 6”x8” liquid crystal display (LCD) electronic flight information system (EFIS) display screens, set five abreast, completely dominate the front of the cockpit and are supplemented by two, lower, Thales flight management system (FMS) computer display units (CDU).

Just below each FMS CDU is a small numeric pad that allows each pilot the ability to control the entry of digits into each virtual control panel (VCP) located in the lower part of the EFIS multi function displays (MFD) with ‘on screen’ boxes detailing NAV 1/2, COM 1/2, Transponder 1/2 and other selections. This removes the need for a separate radio management unit (RMU) and is a system that I much prefer because of the way in which it centralises vital information for the pilot within his/her area of regard.

The central EFIS screen acts as the engine and warning display (EWD) and shows engine data, aircraft system synoptic pages, electronic checklists, system failure warning messages and corresponding automatic ‘pop up’ abnormal/emergency procedures. The outboard EFIS screens, on either side, are the Primary Flight Displays (PFD) and support an attitude based aircraft flight symbol and cross-pointer flight director (FD).

The central power lever quadrant also looks like that of a modern jet airliner with the combined parking brake/emergency brake lever, power levers, condition levers and flap lever (0/15/25/35) all contained within an elegantly neat and clean installation. The condition levers feature integral lights to indicate the correct lever to close in the event of engine fail/fire and are gated at AUTO = Np (propeller speed) automatically governed as per pilot selected power mode (TO/MCT =100% Np and CMB/CRZ = 82% Np) or MAX = 100% Np irrespective of selected power mode. The engine power levers have rear triggers to protect the gate into the ground idle/reverse range and the forward quadrant has spring detents at take off (TO = approx 90% TQ) and at go-around (GA = approx 100% TQ) before the final mechanical limit of approx 115% TQ.

In the event of an engine failure during take off, with the power levers set at the TO detent, the ATR has an automatic autofeather of the dead engine and an automatic torque (TQ) ‘up trim’ of the live engine up to 100% TQ without the pilot needing to move the power lever of the live engine forward from the TO detent, and an auto-rudder trim function to balance the yaw generated by the asymmetric power.

The flight director (FD) and autopilot (AP) flight mode panel (FMP) mounted centrally on the grey coloured glare-shield is well laid out with function buttons and knobs logically grouped and differentiated by tactile shape, colour and position. My only recommendation would be to move the speed control panel, presently set outboard of each PFD, up to join the main FMP so that control of all the FD/AP modes are glare-shield mounted. FD/AP flight and power modes are now shown armed or active in separate and designated flight mode annunciator (FMA) columns in each PFD, just as they would be in any modern Airbus-like aircraft.

Power modes are pilot selected TO/CLB/CRZ/MCT on a centrally positioned rotary switch on the cockpit front face, meaning that the pilot flying (PF) does not have to move the power levers away from the TO detent starting from the take off roll up to the point of descent, if required to retard them, or on the approach. The aircraft does not have auto-throttle (AT) but does have FD/AP indicated air speed (IAS) mode that can be FMS programmed/controlled.

The digital cockpit now supports TCAS II, EGPWS, terrain mapping, a RNP 0.3 navigation standard and aircraft communications addressing and reporting systems (ACARS).

The aircraft is Cat II ILS certified as standard and this can be upgraded, as an option, to a Cat IIIA ILS (50ft radar altimeter decision height) capability. Other avionic improvements in development at ATR for the -600 series include a satellite based approach system (based on EGNOS or WAAS) and ADS-B. The aircraft is certified for steep approaches, including Lugano in Switzerland.

The trailing link main landing gear is carried in fuselage-mounted side pods granting it very soft touchdowns and avoiding the complexity of ‘long’ main gear legs when they are mounted in high wing engine nacelles. The ATR -600 series has a demonstrated crosswind landing capability of 45 knots and ATR is in the process of certifying the aircraft to land with up to 20 knots of tailwind – a simply staggering set of operating limits!

 

 

Flight evaluation

 

My safety pilot was ATR chief test pilot Eric Delesalle on the right hand seat and project flight test engineer Jean Piatek on the central jump seat. I would take the left hand seat and fly the complete sortie.

My single objective was straightforward; having never flown an ATR aircraft of any type before and arriving almost directly to the test aircraft at Toulouse-Blagnac with absolutely no cockpit familiarisation and only a very short pre-flight briefing, could I forget that I was flying a turboprop and simply believe I was operating the latest type of 21^st Century aerospace airliner?

The zero fuel weigh (ZFW) of F-WWLY was 12,000kg and with 3500kg of fuel our ramp weight was 15,500kg. The ATR42-600 has a max take off weight (MTOW) of 18,600kg and this is allied to an almost unbelievable max landing weight (MLW) of 18,300kg! Blagnac OAT was 19C and QNH 1021hpa. Take off speeds were V1 =105kts, Vr =105kts, V2 = 112kts.

The ATR 42/72 does not have an APU, to save weight and reduce cost, but instead uses an electronic propeller brake activated on to the right hand engine (hotel mode).

Engine start was straightforward with each engine stable and fully set just 30 seconds after start selection. The electronic checklists were short and simple to follow and this all added to the real impression of a paperless cockpit. The avionics and aircraft were rapid to programme and configure and there were no ‘first flight of day’ additional checks. As crew, we wore Senneheiser noise cancelling headsets, which made the flight deck almost unnaturally silent.

Take off is always made with flap 15. The -600 aircraft is protected by a take off configuration warning system (trim, park brake, flaps, power management) that can be seen as another advanced aircraft safety feature. The rudder is effective from around 60 KIAS, so nose wheel steering using the tiller is utilised up to that point.

The power levers were advanced by me from a rolling start in a ‘slam’ type action up to the TO detent and the aircraft regulated the power in a completely jet-like way. In fact the ATR42 -600 series delivered its power in such a smooth, linear and predictable way throughout the evaluation and in all flight phases, that I really did feel that I was flying a jet. Also, because the power was so well balanced it actually felt as though the total power was coming from a single source rather than from two, which in part may also be due to assistance from the sideslip cancellation function associated with the auto rudder trim function (as activated through the yaw damper). Along with the excellent tactile feedback granted by the power levers in relation to the power quadrant spring detents, the ATR42-600 had the best/most easily regulated power response of any twin turboprop (large or small) that I have ever flown.

During the take off roll the aircraft required just the merest hint of right rudder to keep straight once the tiller was released. V1/Vr was reached in a very respectable 20 seconds after brake release. Trim changes with gear/flap retracting were minimal. The FMS (magenta) speed bug was followed in manual flight at 160 KIAS in IAS mode towards our level-off altitude of FL200

The ATR has mechanical controls with the ailerons and rudder each being operated through a spring tab and the elevator through a balance tab. Lateral roll control is supplemented by a hydraulically-actuated spoiler (one per wing) acting in conjunction with aileron position. Control mechanical characteristics were good in all axes, with no freeplay, small breakout, excellent centring, light control forces, well harmonised and adhering to the classic control force ratio (aileron: elevator: rudder) of 1:2:5

FL200 was achieved 20 minutes after take off. Vmo at FL200 is 250 KIAS then converting to Mmo of M0.55 up to the service ceiling of FL250. The stabilised cruise speed of 204 KIAS we achieved gave a true airspeed of approximately 300KTAS. During the climb and at all times and in all flight modes, the digital cockpit, the EFIS displays, the FD/AP FMP selections or FMS inputs etc, allowed me to completely believe I was operating a latest generation, Airbus-like aircraft.

Returning to FL150 we set up for un-accelerated, power idle stalling. Our first stall was clean (flaps 0). The PFD showed visual indication of stall approach by a solid red line on the PFD vertical speed tape. Stick shaker started at red line speed tape entry at around 105 KIAS and was supplemented by an audio ‘continuous stall warning tone’. Had the AP been engaged during approach to stall, stick shaker activation would have automatically disengaged it. A positive, spring-assisted, stick pusher activated at 97 KIAS.

A second stall was conducted with the automatic stall protection system (shaker and pusher) manually turned off. Here, distinct aerodynamic buffet occurred at around 98 KIAS with a clear nose drop occurring at around 95 KIAS and without wing drop. However, the effectiveness of the automatic stall protection system was evident and with the system re-engaged for a flap 35/gear down stall, stick shaker occurred at 82 KIAS and stick pusher at 72 KIAS with no wing drop. Applying power as a ‘slam’ up to the TO detent in the stall recovery was again delightfully easy and height loss was minimal.

Before recovery back to Blagnac, I set up the aircraft in a climb, manually flown, flap 15, at TO power, 117 KIAS (V2 +5kts), with yaw damper engaged and had Eric rapidly close one of the engine power levers to idle. The result was – absolutely nothing! Apart from me lowering the nose slightly to follow the FD in speed command, the rudder auto trim system had completely and instantly taken care of the asymmetric yaw. It was truly an amazing demonstration.

For recovery to Blagnac, we set up for ILS/go-around runway 32R. Once again, the level of avionic sophistication regarding such things as FMS set up, selection of COM/NAV, FMA indications on the PFD, navigation displays shown on the MFD, etc, was equal to any of the latest generation of jet airliners. Vref for our weight of 14,900kg was 95 KIAS.

Go-around was initiated by pressing the go-around button in the centre of the side face of the power lever and pushing the power levers through the TO detent and up to the GA detent, with flap and gear following in stages. Once again, a high workload event in older jets or older turboprops was made to look easy.

Our final landing was made from a pseudo steep approach to runway 32L. The EGPWS was re-datumed by pressing the small ‘steep approach’ button on the side panel and the condition levers set to MAX (100% Np). Vref of 95 KIAS was then held manually in a 5.5 degree visual descent. The aircraft felt very speed stable and from a 35’ flare I made a soft touchdown (unusual for a test pilot) into a ground roll of no more than 400m using reverse power and virtually no brakes.

On shutdown, after a 1 hour 20 minute flight, we had used just 730 kg of fuel

 

• Conclusion

 

The test objective I had set myself was easily answered; from literally the first point of slamming the power levers up to the TO detent at the start of the take off roll, the ATR42-600 looked and felt like a 21^st century airliner that just happened to be designated as a regional transport aircraft and which was equipped with a propulsion system that provided simply the smoothest and most easily controlled power response of any twin turboprop aircraft, of any type or size, that I have ever flown. This feeling never left me during the evaluation.

The ATR-600 series will be an undoubted success and one that, I predict, will have many airline executives examining their present fleets of regional jets as the expense of jet operation starts to bite and when a new generation ATR turboprop starts to make those jets look outdated!