Airtest – Citation VII

Even more surprising was their resolve to retain the Citation appellation for their new, quite different, bigger, faster, long range, supercritical swept winged, mid size eight seat jet. This Cessna 650 was given a sub model number but, confusingly using one right in the middle of all the others, they called it the Citation III.

After selling over 200, the Citation III evolved into the current Citations VI and VII, but all that these sleek machines have in common with their straight winged siblings are good value, extreme internal and external quietness, easiness to fly and absolute simplicity of operation. Cessna defend their designation decision, maintaining that the obvious connection with the well regarded Citation family more than makes up for any confusion. Regardless of this, these later swept wing Citations certainly compete very successfully with the 125, Falcons and Astra forstand up comfort, high speed and reasonable range at a price below the Gulfstream and Challenger.

The Mark VII has distinctive lines and Cessna’s demonstrator looked smart and sleek against a granite grey sky and driving icy rain on the damp ramp. Adolphin like nose and tern shaped wing root fairings add a natural grace to lines more curvaceous than most, showing how, after 90 years, we are at last realising Nature’s complex forms persuade their way through fluids better than our more easily produced geometrical parodies.

I was introduced to it by the company’s demonstration pilots Ray Wellington and David Moore, with whom I was to fly. Starting at the front, David explained that the blunt nose is there for a purpose, a sharper one would collect ice which, when shed, might nip smartly aft and nobble the motors. The new all glass laminated windscreens have a rain repellent coating and for ice protection are now electrically heated by frequency wild AC power from a pair of dedicated generators. The 30 by 22cm side windows usefully open and the main screens have bleed air rain removal and ‘rain augmentation’ deflectors.

The comparatively thick supercritical wing, like the engine intakes, has bleed air anti icing for its polished leading edges. The whole trailing edge not devoted to ailerons is occupied by the six section, electrically driven, single slotted, Kevlar and graphite composite Fowler flaps. Earlier Citation IIIs had a history of flap maintenance problems, and their pilots developed the habit of leaving them parked in the takeoff setting so that they could at least be ferried for repair if they jammed. This is no longer necessary with the VII, which has new motors and stronger tracks under four neat fairings per side.

The wing’s light, bonded and riveted structure contains 3350kg of fuel, its tank extending into a big elongated aerodynamic belly fairing with new protective ventral skids. There are no doors over the twin main undercarriage wheels but the legs are so enclosed, making both Vlo and Vle 210kt (390km/h). Although its 2. 7m track is narrower than the early Citations, this model has the superior trailing link suspension.

The truly towering 2. 6m fin (unusually lacking a dorsal fillet) suggests good yaw stability and directional control and needs no de-icing. It and the highly swept tailplane have bird splitters hidden behind their leading edges, the tailplane’s being antiiced by the same AC generators as the windscreens’. Elevator and rudder are manual but the tailplane has electrically variable incidence (AC with DC backup) and 3° of anhedral.

The shoulder mounted Garrett TFE731s are set high to minimise interference drag, so the aeroplane carries a cabin nearly as big as the 125-800, but faster and more economically. These-4s are hybrids optimised for this application, using the kinked high altitude fans of the -3B with the hot section and directionally solidified, cooled turbine blades of the 5. Producing an impressive 4080lb thrust, they run at low temperature, endowing long MPI (major periodic inspection) intervals of 2100 hours, and have rudder bias from a bleed off the good engine in the case of failure. Automatic performance reserve (APR) is also used, temporarily thrashing more than certified power from the live engine if the other quits. Rohrreversers are standard, single engine reverse is permitted, and the new ‘sugar scoop’ aft inner fairings reduce drag and stop tail buffet in reverse. There are two alternative APUs (this one being the quarter million dollar Garrett 36-150/w which has no hydraulic pump). Both it and the Turbomach T-67-40C3A unit can be started in the air up to 20,000ft and used at 30,000ft (6100m and 9150m) or below.

Below the left nacelle a 64cm wide, lockable, drop down door opens on the 1. 73m3, lit, heated and carpeted but unpressurised rear baggage compartment which takes 920kg of bags (or 1543kg without the APU). This is much more accessible than most, with a sill only 1. 2m high and very useful steps sensibly moulded into the back of the door. There are similar steps in the fold down main entry door.

In the cockpit Cessna has retained much the same uncomplicated layout as on earlier Citations, with circuit breakers on the sidewalls and a clear roof. Reflecting the move away from its little kin into the two crew big league, the landing gear lever is now on the copilot’s panel and the flap selector by his left knee to the right of the centre console. A full sized speed brake lever runs to the left of the throttles, in the same quadrant, its percentage graduated indicator combined with the flaps’ on the right. Above the raised speed brake lever, in line with the ‘piggyback’ thrust reversers, a yellow spoiler lever pivots with the reversers for maximum lift dumping on landing.

Primary instrumentation is by four tube Honeywell EFIS with 12 by 15cm screens supplied from dual AHZ-600 fibre optic AHRSS (Attitude and Heading Reference Systems, a sort of slightly less rich man’s laser ring gyro platform) and dual digital ADCs. Each upper EADI screen displays horizon, tum indicator, ILS, radio altitude, AP/FD flight mode annunciator, director chevron, numerical IAS with trend arrow, digital VSİ (also with trend vector) and fast/slow adviser. The lower EHSIS have compass rose, arc, FMS or map modes showing VOR, FMS or ADF pointers, wind indicator and ground speed or time to waypoint (the latter three modes will also show FMS derived route and weather radar information). Unfortunately the associated course and heading knobs are rather remotely situated at the rear of the centre console.

The captain also has an AoA indicator calibrated in decimals of max CL, and this particular aircraft has the optional fifth centre panel screen for the Primus 870 doppler radar picture. Twin outboard audio sub panels allow access to the Collins ProLine II radio package and the single King KHF-90 HF.

Secondary instruments (including the not so unimportant ASI/ Machmeter, RMI and altimeter) surround the CRT’s. To be honest I do not like these combination set ups, never knowing quite where to look for the required information in a hurry, preferring either a proper single screen Primary Flight Display or traditional round clocks. However, this layout undoubtedly looks impressive to the man who has put down the money when he glances through the door to inspire the workers.

When he does this he can see the flight deck sharing some of the cabin’s elegance with dark taupe top grain leather padding on both sidewall ledges (each with two cup holders) and seats. These have Pacific Scientific five point inertia reel harnesses, and are fully adjustable using three neat little orange balls on the mid screen pillar for eye alignment. The rudder pedals have simple three position adjustment.

A long annunciator spans the top of the centre panel, with fire detection and control in the glareshield above it. Standard Citation vertical tape powerplant gauges have digital readouts below and clear green, orange and red markings so you only have to remember limitations for the week you sit your type technical exam. Below the mid main panel is the Tilt Panel’ with most primary system switches.

N712CW has an empty weight of 6220kg (well above the stated ‘standard’ weight of 5293kg which ignores decor, seats and fittings). Carrying 1960kg fuel as displayed on the tape gauges and totaliser, two passengers and 100kg of freight, we had an all up weight of 8602kg. This is comfortably below the 9072kg max landing weight and well within RTOW of 10,138kgs. Ramp weight can be set in the totaliser so that gross weight is accessible throughout flight by a flick of a switch.

Starting is dead simple. Push the button, check for 10% N2 (which takes three seconds) and fan rotation, lift the latch and raise the thrust lever to idle. The whole process took 25 seconds with a peak ITT of 570°C, well inside the 95°C maximum. David shut down the APU with his side panel controls and activated all systems within two minutes to carry out the checks later, during the taxi. With engines running the interior was noticeably quiet, while the microprocessor-controlled electronic pressurisation came on undetectably. This normally uses one pack for the cabin and the other for the cockpit but either pack can condition both together.

Releasing the aft console park brake, with 40% fan rpm to break away uphill, I found the sensitive spring loaded hydraulic nose wheel steering had a very, very brief lag causing a slight snaking tendency in the crosswind. It will turn through 75° using the small left armrest wheel and through 6° with the rudders. Noticing a little bit of bump thump from the nose oleo on Biggin’s old concrete slab taxiway and a very slight waddle from the near-silent trailing link main legs, I thought the undercarriage generally excellent. The brakes were great too, very powerful if needed, but gentle when pressed lightly and they did not snatch like so many others.

Using twenty flap for takeoff, we extracted and bugged a pre computed N1 of 99%, with 118kt (219km/h) for VI, a 121kt (224km/h) rotate speed, 131kt (243km/h) V2, flap retract at 156 (289), and a single engine climb speed of 165 (306). David armed the APR and, after a comprehensive briefing covering who would do what and when, particularly in an emergency, his final words before takeoff were “. . . and don’t forget to enjoy yourself?” As advised, I increased power to 70% to prevent slow acceleration asymmetry. Although engine noise could at last be heard as the rpm rose, this immediately dropped to almost nothing as we started to roll. Superlative takeoff performance is part of the type’s specification so we positively squirted along Biggin’s Runway 21, 90kt (167km/h) coming up in under ten seconds and rotation after just 16 using under 1000m in a wind of 240/20-30 (well within the 25kt (46km/h) max demon- strated crosswind component). The flight planning guide quotes azero wind FAR Part 25 field length of 3780ft (1152m). Staying straight was simple, the nose wheel steering seamlessly blending to more than adequate aerodynamic control.

Pegging 10° nose up, I found rotation easy with the lovely light elevators, pitch control seeming well damped, with neither over swing nor any tendency to over control. The gear flicks up in six seconds and I soon felt the promptly engaged yaw damper using the rudder to combat the turbulence. I was barely aware of the flaps retracting without any noticeable trim change under half a minute from start of roll. We were level at 1500ft (451m) and turning within one minute.

Wanting to go to the West Country at 41,000ft (12,500m), ATC had us level at 1000 AGL flying a 270 overhead, to route due east via Detling. All of which was excellent IF practice for someone who flies a jet takeoff once per month, had never touched the machine beforeand shot into the 200ft(60m)overcast at 3000fpm (915mpm). That it was even possible speaks volumes for the aircraft’s excellent controls, stability and easy-to-assimilate instrumentation (and David’s trusting nature). Once unfettered by ATC, we soared heavenwards at nearly 4000fpm (1220mpm) at 250kt (463km/h), increasing to 300 (556) above 10,000ft (3050m). (Vno is 275 [510km/h] to 8000ft (2440m) and 336kt [623km/h] above this, reducing linearly to 278kt [515km/h] at 36,500ft [11,132m), with a pilot switchable ten knot [19km/h] increase if zero fuel weight is below 6963kg [15,350lbs)). Initially we used 93% fan rpm, to the occasional woodpecker like accompaniment ofthe stabiliser trimmer, later transitioning to 101% fan rpm once the OAT dropped below-15. Thereafter, we simply let the engines’ Digital Electronic Engine Controllers (DEECs) maintain climb power within limits.

This stimulating performance derives from the improved hot and high capability requested by Citation III operators polled by the company early in the design process. They also wanted (and got) greater range from 1500m runways, more robust flaps, better windscreen de-ice and a host of smaller refinements.

When I had sufficient spare brain cells to assess the handling, I found the controls really nice, fingertip light and effective. The ailerons are heavier without their hydraulic power assistance, but no worse than on some old airliners. Roll rates are even acceptable without the spoilers (which normally extend on the down going wing to assist when the ailerons are deflected more than 3%) provided you put enough effort and deflection into the squared off yokes. The pushrod and cable manual elevators were light and lovely, and the rudder with its series yaw damper was as heavy and dead feeling as on other, similar machines.

Engaging the autopilot in speed mode, I found it held IAS (Indicated Air Speed) well and turned gently to maintain heading or intercept an FMS (Flight Management System) track. A half bank mode gives even more gentle turns and the VSI mode is protected against over speeding. This autopilot has one unusual feature. If cabin altitude is sensed as climbing above 13,500ft (4120m) at an actual altitude of 34,270ft (10,452m) or higher it will turn the aircraft through 90° and lower its nose to maintain 10kt less than Vmo down to 15,000ft where it will level off. This guards against crew incapacitation in a decompression, but does assume they will stay awake long enough to at least close the thrust levers (and preferably raise the speed brakes too).

We reached FL390 over Dorsetin under 20 minutes, despite several intermediate restrictions, using 400kg of fuel. David said that, from a gross weight takeoff, 24 minutes and 480kg were typical for a climb to FL 410 (12,505m). After using 1315kg of fuel from each wing tank (and before burning 1135kg) the fuselage tank can be emptied using its two electric pumps. Drifting up to FL 430 we accelerated to Mach. 77 for a TAS of 430kt (798km/h) with a 595kg/hr fuel flow. Cessna quote 442kt (819km/h) and 525kg/hr at our weight. After 16 minutes Mach will build to . 83.

This aircraft is designed to get above 40,000ft quickly, going straight to FL 430 in ISA from a max weight takeoff. Its operating ceiling is a usefully high FL 510, while Mmo is now . 83 Indicated Mach Number (IMN) from the improved Air Data Computers, rather than the Citation III’s . 851 IMN, although actual speeds are identical. With its small Mach induced drag rise, the supercritical wing is normally driven at its . 83 Mach design speed using the 924 ITT limit for a book TAS of 452kt (838km/h), burning 525kg/hr. This is faster than any but the biggest and most expensive corporate charabancs and surprisingly little fuel is saved by going slower. The Citation VII really is happiest going high and fast.

With two crew and five passengers this high speed cruise allows a flight of just under five hours with 45 minutes reserve, using 2900kg of fuel to cover just over 2000nm (3710km). While this is quick, the range is hardly trans Atlantic, nearly 700 miles less than the worst of the opposition and 900 miles below the Astra SP.

The reason lies in the type’s past. The original design had a bigger fuselage fuel tank but, during development in the late seventies, a number of serious airliner accidents ensued from loss of control following damage to major systems after uncontained engine failures. Investigation revealed potential flaws in many contemporary designs, so the FAA was spurred to introduce sweeping new restrictions to FAR Part 25. These covered the routing of flying controls, their supply pipes, fuselage fuel tanks and lines, and anything else aboard that might be vulnerable to dynamic engine failure.

Very unusually, but courageously and commendably, these regulations were made retrospective and the poor Citation III, in mid development, was right in the damage plane of the new legislation because its tank was in the cone of vulnerability. The only solution was to shorten the fuel cell, losing over 500kg of fuel and irrecoverably reducing range by nearly 13%. (Although even the original tankage was not over generous). Later models were helped by more economical engines, and the derivative Citation VII does the best it can within its certification to Amendment 39 of FAR 25, but the problem will only be permanently solved with its Citation X descendant, due for first delivery in September 1995.

The aeroplane flies every bit as nicely at high altitude as it does at lower levels. Even without the yaw damper it is directionally pretty stable, although a gentle foot on the rudder pedals helps reduce any induced weaving. Whack in a dollop of aileron and itrolls smartly. Let go of the wheel and it stops. Just like that. Smashing! Displaying the expected excellent Citation visibility, an initial surprise was the remarkable cockpit quietness. A glance at the low 194kt IAS (360km/h) helped explain that. The safe envelope is very wide, even at FL500 (15,250m), where the margin between red line (this wing has no Mach buffet) and 1. 5glow speed buffet is a whopping 75kt (139km/h). It has never heard of coffin corner’. Re-engaging the autopilot allowed me to move aft and explore the passengers’ accommodation.

The Citation VII specification excludes the interior, a designer helping the purchaser exercise his sense of style by selecting his own at Wichita’s Citation Completion Center, where he can take his pick from the many options on display. A ‘Goldilocks’ area even lets him sample cushioning, to feel whether it is ‘too soft, too hard or just right’. Computer graphics simulate the selected cabin furnishings in detail, the software so sophisticated that a proffered fabric sample can be read, absorbed and displayed with other textures, tones and trim for the rest of the interior. Normally accommodating seven passengers and capable of cramming in up to 13, this particular machine holds six in a ‘club and a half layout with the middle four facing each other and the rear pair looking forwards. The central aisle has a 175cm (5ft 9in) headroom, and is about a 30cm below the side floors with their six well stuffed, dark taupe top grain leather seats. Each has its own eye level window with pull up blind, individual brushed aluminium light, air outlet and cup recess (which will take a flip top fireproof ashtray). All seats recline and swivel and have retractable headrests and taupe inertia reel diagonal straps to supplement the belts, while the two facing pairs bracket two section maple edged, marble topped folding tables. All but the rear seats swivel through 180%, while the central right side position has lighting and temperature controls and a Flitefone handset in its inset marble side ledge. This ledge extends forward of the aft facing front right seat to a wide ‘lowboy’ adjustable shelf food tray stowage and drinks cabinet. Furnishings end with a magazine rack low on the bronze polycarbonate rear wall.

The cabin is near silent in flight, endorsing Cessna’s claim that this is the quietest mid size jet. A normal voice conversation is easily conducted from one end of the cabin to the other. Comfort is so extreme, with so little vibration or movement that, if you closed your eyes, you could be parked on the ground. Even right at the back in the lavatory there is only a minute level of engine noise, soon drowned in the comparative roar of the flush. If I dared venture a criticism, it would be having to negotiate the 30cm aft cabin step over the under floor spar before entering the toilet. Like the poor range, this shortcoming will be addressed in the forthcoming X.

Back at the workers’ end I was shown the normal descent, clean, at 3000fpm (915mpm) using 95% rpm until IAS increases to 300kt (556km/h). A much steeper one mile per thousand feet (1. 6km per 305m) angle can be achieved at 4500fpm (1373mpm) with idle power,. 75 IMN and 220kt (408km/h); while using the incredibly smooth speed brakes causes a very noticeable deceleration and increases the rate to near 8000fpm (2440mpm). There are four hydraulically actuated spoiler panels on each wing upper surface; the outer ones assist the ailerons, the middle pair are fully modulatable speed brakes and all four per side risefor after landing lift dumping or a 20,000fpm (6100mpm) emergency descent. They can all be raised at any speed between Vmo/Mmo and 150kt (278km/h), but the speed brakes’ minimum speed is Vref +15.

The Citation VII’s stalling manners are quite remarkable. Despite its narrow swept wing it handles just like its junior stablemate. Considerable thanks are due to NASA’s remarkable Dr Richard Whitcomb, who devised the current generation of supercritical aerofoils. Quite thick at mid chord, with rounded leading edges, reduced camber and flicked up trailing edges, these delay the onset of critical supersonic flow to a comparatively high Mach number. Coincidentally this shape gives excellent low speed handling, so the Citation VII needs no stick pusher like some old fashioned jets and only sports small, mid span, leading edge fences and a row of vortex generators to energise the airflow ahead, surprisingly, of the outboard spoilers rather than the ailerons. There are also three stall wedges along each leading edge.

At top weight the aircraft stalls at 126kt clean and 102kt with full flap. We were unable to leave controlled airspace in the time available, so my investigations had to be made on the descent, and confined to recovery from the initial symptoms. At 7700kg, after the undercarriage warning hom at 165kt (306km/h), the single, left side stick shaker started rattling at 135 (250km/h) and, immediately applying full power, we quickly accelerated away. The book speed for the actual stall at this weight is much lower, at 111kt. With gear down and full flap, shaker speed was depressed to 110kt (204km/h) and handling was entirely normal, while the published stall speed is a remarkably low 90kt (168km/h). Flaps are retracted to 20 for recovery, full power driving the aircraft away.

Throttling back an engine at 200kt (370km/h) and 11,000ft (3355m) with full power (98%) on the other, we still climbed with ease and only moderate foot loads. Descending into cloud at 900fpm (275mpm), an OAT of 9° required engine ant-ice on. This needs around 70% N2 to be effective, but speed brakes can be used to keep the descent going.

An FMS driven needle can be selected to point at the airfield; the FMS gives a distance to run read out, and the flight director is available to assist. Flap limit speed is 210kt (390km/h) for up to 20° and 170kt (315km/h) for full flap, so I called for flap seven at 200kt (370km/h) and twelve miles out, feeling a slight nose up pitch as we descended to 4000ft (1220m) to intercept the ILS. Twenty flap induced a useful pitch down and, taking the gear at one dot above the glide slope, I noticed it lock down after about four seconds.

We ran full flap (37%) at half a dot on the ILS with another slight nose down pitch. Nailing the glide slope on passing 3000ft (915m), 70% fan rpm gave a 500fpm (153km/h) descent in the strong headwind, although David said 60-65% is more usual. At our 7720kg (17,000lb) weight the Vref was 122kt (226km/h), and he recommended that I anticipate the shear and aim for 135 (250) in the reported 230/15gusting 25′ (28 to 46km/ h) surface wind. (Maximum crosswind is 25kt [46] with or without reversers, but only 10kt (19km/h) if the roll spoilers are w/s).

The useful radio altimeter is required for Cat II, and it comes to life below 2500ft (762m) with the half sensitivity enhanced localiser for precision guidance. I found the Citation remarkably easy to control, lovely and stable despite the unpleasant conditions, power adjustments causing little trim change and speed never varying by more than a couple of knots. At three miles on final the EFIS wind readout said 262/28 (52km/h) and the EADI’s rising runway started to appear at 500ft (150m). Although we had briefly glimpsed the fiery cross of approach lights through ragged cloud a few minutes earlier, we were then in solid muck to 50ft (15m) above decision height.

David was restating the go around procedure as we blundered out into the murky wind swept, rain puddled twilight, seeing the runway lights coincidentally with the synthesized voice’s “Minimums, minimums”. Despite David’s prompt, I needed no reminder to retain the ten knot (19km/h) margin over Vref down to the concrete in these challenging conditions, still finding it easy to position the aeroplane without any over controlling or wing wagging. Nearing the deck I was concentrating too hard to absorb his advice to “Land flat, don’t try to flare it, let the gear take the strain”. Flaring normally while smoothly tapering off the power, I found that at this height, with the wingtips only four feet up, any excess speed will keep the machine airborne in its powerful ground effect.

After a brief float, I put it down positively, the excellent main legs completely absorbing the level attitude touch down. Promptly lowering the nose wheel, I only raised the speed brakes, David cautioning me against use of lift dump because of the adverse effect on roll control in the crosswind. Meanwhile my pneumatic reverser conditioned right hand rediscovered that hydraulic reversers need a relaxation of the upward pressure on the levers at the interlock to achieve spool up. I just kept on pulling and got nothing. Nevertheless an early dab on the brakes quickly dissipated our speed. These refreshingly progressive units have lots of stopping power in reserve, while remaining easy to modulate for a gentle turnoff at the far end. We used less than a thousand metres without reverse, the book figure at max landing weight and sea level being 887m (2910ft). Landing and rollout were easily controlled, despite less than perfect conditions and my complete unfamiliarity with the aeroplane. It seemed stable, responsive and particularly easy to fly. This handling simplicity won the Citation family the 1986 Collier Trophy for a superlative safety record.

On shutdown after Ihr 20min flying we had used 950kg of fuel. My abiding impressions of the Citation VII are of an excellent cockpit layout, super handling, rocket like performance and remarkable quietness inside and out. Cessna quote 69. 3 dba on departure with 84. 8 dba on the approach, and have approval to operate the type from dozens of neighbourhood airports where jets are normally banned. Personally, I think few non flying locals will ever notice the thing because, as we were leaving, the hussssh of its next takeoff was quite obliterated by the clatter of a starting Arrow a 100ft away.