Fighter Aviation Topics, Page 5

 

"Flying the F/A-18F Super Hornet", Part 2 (First published in May and June 2001 Australian Aviation.)  by Dr Carlo Kopp, PEng Carlo.Kopp@aus.net  © 2002, 2001, Carlo Kopp February 2, 2002   2 Part 2 A Cockpit Perspective One of the privileges of being a defence analyst and writer is the occasional opportunity to indulge in flying some very interesting aircraft. This Avalon airshow Boeing very graciously invited me to partake in the pleasures of flying the F/A-18F Super Hornet, equipped with the latest revision of the digital flight control system. The aircraft far exceeded my expectations in both handling qualities and ease of cockpit use.  The aircraft flown, BuNo 165797, was one of a pair of production aircraft brought out to the Avalon airshow, and operated by the US Navy at NAS Lemoore for weapons delivery trials. In terms of configuration these aircraft were equipped with a unclassified software load, designated 18EI "V".  The cockpit configuration of these aircraft represents early production status, using cathode ray tube MultiFunction Displays (MFD, formerly Digital Display Indicators or DDI) for the left and right cockpit displays and touch sensitive Up Front Control (UFC) panel, but full colour AMLCD panels for the centre moving map display. The aft cockpit had the centre MFD installed above the UFC panel.  Production configuration aircraft will have the aft cockpit UFC installed above the centre colour MFD, with growth variants using a much larger 8 x 10 inch AMLCD display for tactical situation data and moving maps. The aft cockpit does not have provisions for displaying HUD camera video on the UFC or MFDs. Modes for the MFDs are all selectable by pushbuttons on the bezels. Production aircraft will use high resolution colour AMLCD panels in all displays, including the UFC.  The cockpit layout follows the basic style of late model F/A-18C aircraft, with an improved engine and fuel status display. Pilot feedback saw Boeing restore a rotary switch for the `bingo fuel' setting on this panel.  The controls are standard stick and throttles, with mechanical linkages between cockpits for all but the rudder pedals. Mode controls for the weapon system are all incorporated in the HOTAS (Hands On Throttle And Stick) controls, in addition to a master mode selector switch for A/A or A/G in the upper right of the cockpit. A single switch is also available to disable all aircraft electronic emissions from a single point, under EMCON conditions.  Like other modern Boeing cockpits, the system is very easy to operate with well laid out mode select controls, and the capability to display any format on any particular display. We flew the aircraft with the left MFD configured as a HUD symbology repeater, the centre MFD as a moving map with overlayed navigation symbology and compass rosette, and the right MFD as the radar display.    2.1 Flying the Super Hornet My demonstration pilot was Dave Desmond, Boeing's Chief Experimental Test Pilot on the F/A-18E/F program and a former US Marine Corps F/A-18A-D operational pilot, who has flown every USN/USMC Hornet model since 1981. During the Super Hornet flight test program he performed much of the high G handling tests for the aircraft with various load configurations. The dazzling Avalon flight demonstrations were flown by Boeing Senior Experimental Test Pilot Mike Bryan, a former USN operational pilot.  Preparation for the flight was meticulous, with 1.5 hours earlier in the week dedicated to G-suit and helmet fitting, and a 2 hour preflight briefing which included detailed discussion of emergency handling and aircraft recovery procedures should an ill behaved avian find its way through the windshield.  Two areas were available for demonstration flying, an overwater corridor south of Avalon and east of King Island for supersonic runs, and a `Hornet Box' east of Colac for overland flight demonstrations. Both were loaded into the computer and displayed on the moving map, a very convenient feature once airborne. Weather conditions were cool, but clear with very little cloud cover, ideal for a VFR sortie. The aircraft configuration was very light, with full internal fuel and all stations empty.  The plan for the sortie was to demonstrate some of the aircraft's handling characteristics and avionics, with the caveat that my very few hours of recent aerobatic time would set bounds on how much we could explore the envelope. Needless to say, 2 second increments of 5.5 G on a 200 HP Z.242L piston aerobatic trainer set limits on how much manoeuvre tolerance you can gain in a hurry!  After the customary preflight walkaround I was strapped in and hooked up, upon which Dave briefed me on the use of the MFDs and UFC. Once Dave strapped in, the APU was started and then the engines. Oxygen is generated by the OBOGS which requires an operating engine. The pretakeoff BIT was initiated on the MFD and the computer waggled all of the control surfaces - we dispensed with the habitual freedom of controls movement test. All bit status information is tabulated on the MFD and all failed BIT tests flagged as `degraded' on the MFD.  With engines turning, cockpit closed and seats armed, we taxied to the holding point and waited our turn in the queue for runway access.  For takeoff, Dave selected full afterburner and rotated at 105 KIAS. Once airborne, we levelled off and accelerated to 370 KIAS for a 45 degree pull up and full power climbout at 250 KIAS. The RoC off the runway was around 27,000 FPM and we climbed to FL200 ft in about 1.5 minutes from brake release. We reached FL260 at 297 KIAS and Dave handed the aircraft over to me with the customary stick waggle, pulling the throttles out of afterburner.  My first manoeuvre was a 360 degree left aileron roll at about 1/2 stick input. The aircraft's response was very crisp and full roll rate achieved very quickly, at about 120 degrees/sec. The roll recovery was a little messy, by force of habit I applied opposite stick to arrest the roll rate sharply and ended up 15 degrees into a right roll before I neutralised the stick position. The Flight Control System (FCS) reacts very sharply to control inputs and is perfectly damped from a pilot's perspective, the aircraft reacts almost instantaneously with G and roll rates proportional to stick deflection, at all airspeeds. Typically one inch of stick deflection produces 2 G of load factor, with very light and comfortable stick force for small control inputs. The Super Hornet can be flown very precisely with gentle control handling, and is very easy to point.  While I maintained heading and altitude at Mach 0.95, Dave lit up the APG-73 and demonstrated the interleaved surface search mode. In this mode the radar interleaves synthetic Maritime Moving Target Indicator (MMTI) tracks with raw video, the latter allowing the pilot to gauge the size of the surface track. We locked up a pair of large transport vessels tracking the coastline on opposite headings. The size differences were clearly evident in surface search mode.  Once we completed the radar demo, Dave suggested I do a supersonic run and explore supersonic handling. I pushed the throttles past the detente into full afterburner and the aircraft accelerated through the sound barrier, with only a gentle bump to indicate that we had gone supersonic, the FCS smoothing out the `Mach dither' very effectively. Ten minutes into the sortie, at 735 KTAS/485 IAS/M1.18 I initiated a half stick 360 left aileron roll, and recovered the roll cleanly. The handling was indistinguishable from the subsonic roll, with a roll rate of about 120 degrees/sec for a half stick input. At Dave's suggestion, I pulled the throttle back out of burner and initiated a climbing supersonic 2.0G heading change to point at 330 degrees to the Hornet Box over Colac. The aircraft turns very smoothly and little stick force is required to hold 2G, virtually no lateral stick input adjustments were required to keep the nose on the horizon. Airspeed bled off fairly slowly despite the applied G and altitude change.  While I maintained heading at 280 KIAS/FL350 kft, Dave selected the Ground Moving Target Indicator (GMTI) mode on the APG-73 and we started hunting for some road traffic along the coastline at about 40-50 NMI slant range. Within seconds a row of tracks appeared across the scope, as expected outlining the Princes Highway near Colac. Some tracks intermittently appeared and disappeared, as trees blocked the line of sight between the radar and moving vehicles. Dave attempted a single target track on at least two targets but the foliage produced repeated dropouts - as much as we tried we couldn't cheat the physics of radar absorption.  We crossed the coastline, `feet dry', to enter the Hornet box.    2.2 The `Virtual Speedbrake' The next handling demonstration involved involved the speedbrake and some high alpha low speed handling, an area in which many fighters experience problems in maintaining direction and avoiding a departure into uncontrolled flight.  The first demonstration involved the `virtual speedbrake' effectiveness and handling in this configuration. The F/A-18A-D, like the F-15 series, employs an upper fuselage hydraulically deployed speedbrake. The Super Hornet has no such device, yet achieves the same effect through what can only be described as `digital magic'. The speedbrake function is produced by a balanced deployment of opposing flight control surfaces, generating drag without loss of flight control authority or change in aircraft pitch attitude.  Dave demonstrated the speedbrake function, and I was asked to observe over the shoulder and in the mirrors the raised ailerons, lowered trailing flaps, raised spoilers and splayed out rudders. Deceleration is smooth and there is no observable pitch change.  At Mach 0.63 Dave invited me to fly another 360 aileron roll, to observe that the aircraft retains considerable control authority despite the fact that the rudders are splayed out, and the ailerons, spoilers and flaps are generating balanced opposing pitching moments. I applied roughly 1/2 stick input and the aircraft very cleanly rolled through 360 degrees at about 90 degrees/sec roll rate. I commented on the lower roll rate and Dave observed that we were significantly slower, he then proceeded to demonstrate the roll again with a full stick input, producing around 180 degrees/sec with a slight overshoot on recovery. The aircraft feels very stable throughout the manoeuvre and there is no observable change in control forces or control input response by the FCS.  The new ATFLIR is a high resolution `midwave' design, which is a generation in technology beyond most of the FLIR targeting pods currently in operational use. This targeting pod will supplant the existing F/A-18C pod set (Photo Boeing).    2.3 High Alpha Handling We then proceeded with some high alpha handling. Entry into this regime involved pulling back the power, while I tracked the control movements hands on, Dave progressively increased the amount of aft stick to maintain a constant airspeed around 90 KIAS. Power is concurrently added to maintain altitude and airspeed, and the aircraft was stable at 43 degrees alpha. Dave then demonstrated a full 360 degree aileron roll while maintaining over 40 alpha and close to full aft stick. Having worked through several manoeuvres, we took at break to explore further radar modes. Dave selected the high resolution spot SAR mode and slewed the patch map over Colac. After several sweeps the image sharpened up and we could resolve individual buildings and streets in the town, clearly contrasted against Lake Colac. The difference in groundmap quality against the sixties technology real-beam mapping APQ-161 truly reflects the 4 decades of intervening technological evolution. Having explored main street Colac for several minutes, we turned our attention to the Avalon airfield. At about Mach 0.6 at FL200 Dave selected SAR spot mapping and slewed the radar over the Avalon parking area. With the nose pointing to Avalon, a few miles east of Colac, we had very little lateral Doppler and at Dave's prompting I slewed the nose about 30 degrees to the right to get a larger angle off the nose. Within several seconds the picture began to sharpen up, and Dave adjusted the patch position so we could observe the corral and pilot's hut from whence we had departed less than an hour ago. It took little effort to resolve the parked aircraft and the hut, the fence posts along the runway resonated nicely and we got a clean row of dots across the picture. Exploring the image, the fields full of parked cars were easily resolved, as were the row of chalets, the control tower and taxiways. Picture contrast was excellent and the synthetic image was highly stable.  An attack with a glide weapon like an AGM-154 JSOW or winged GBU-31/32 variant would be very easy to execute with a delivery accuracy of mere feet, in zero visibility conditions, using this mode.  Dave handed the aircraft over and I flew several gentle 1.5G turns, while we discussed the control forces and required inputs per G. Dave switched the radar into real beam mapping mode and pushed the throttles to mil while I pulled the nose up to climb back up to FL280.  I was invited to fly the aircraft into a high alpha regime. I pulled off the power at Dave's instruction and applied aft stick to bleed off airspeed while holding altitude. At about 30 degrees alpha a distinct rumbling sound developed, as the airflow over the aircraft began to break up into turbulent flow, yet the handling did not perceptibly change. Stick force however did increase noticeably, as I approached 3/4 aft stick deflection I needed both hands to comfortably pull the stick back further. Holding 90 KIAS I pulled the aircraft gradually back to 48 degrees alpha, while Dave worked the throttles.  The aircraft was very stable throughout entry and the progressive increase in AoA, there was no perceptible rolling sensitivity in lateral stick inputs, the knife edge balance preceding a wing drop which one would intuitively expect as a result of the aircraft's speed and angle of attack was absent. From the pilot's perspective, the feel is very solid and smooth.  Small lateral stick inputs yielded a proportionate response, there was no perceptible reduction in control input sensitivity in this regime. To exit from the manoeuvre, I released the aft stick pressure, and as the aircraft unloaded Dave pulled back the power.    2.4 Flying the Pirouette The pirouette manoeuvre was developed at the request of operational pilots, as a high alpha low speed reversal, akin in its purpose to the classical yo-yo. In a high yo-yo, the pilot unloads in a tight turn, climbing and decelerating, then rolls 90 degrees and pulls through 180 degrees to reverse direction, leaving the aircraft pointing at the target with an altitude advantage. The pirouette is an `in-plane' reversal manoeuvre which resembles a conventional stall turn or hammerhead in a piston aircraft.  To execute the pirouette at low speed, the aircraft is placed into a high alpha attitude, and as airspeed drops to around 100-200 KIAS and full back-stick is held in, full lateral stick and rudder are applied into the direction of the reversal.  The stick and rudder force for the pirouette entry are light, compared to the aft stick force, and the aircraft very smoothly slices around in-plane, wings level, to point in the opposite direction. The stick and pedal inputs are in effect the same as for a snap roll, but the FCS software senses the attitude and control inputs and executes the pirouette. Without the FCS code designed to do this, most fighters would depart and possibly do so in a direction other than that intended by the pilot.  To demonstrate the pirouette, Dave asked me to take the controls and apply progressively more aft stick to bleed off airspeed. As we hit 155 KIAS, 20 degrees alpha at 1.9G load factor, I followed his instructions and applied full right rudder and stick. The aircraft pivoted around, slowing to 80 KIAS over the top and with controls neutralised accelerated quickly to 215 KIAS coming out of the manoeuvre.  The pirouette is almost ridiculously easy to fly, and the aircraft does so very smoothly, at no point does the pilot feel an impending departure or other loss of controllability.  Having played through the key radar modes and worked through the basic high alpha manoeuvres, Dave was unable to tempt me into the inverted stall and pull through manoeuvre which I had a mere one hour ago looked forward to trying. My lack of currency had been catching up with me, and we agreed it was time to exercise the aircraft through a couple of touch and goes and then call it a day. We departed at a leisurely pace from the Hornet box for some circuits at Avalon.  `The F/A-18E/F Super Hornet is an F-15C sized Hornet, with similar weight, fuel and combat radius performance to the USAF's leading operational fighter. Unlike the F-15C, the F/A-18E is not a design optimised for top end supersonic BVR engagements, retaining the hybrid wing design strategy of the F/A-18A-D and its APG-73/79 radar arrangement (Photo Neville Dawson).'   2.5 Air-Air Radar Modes Enroute to the Avalon circuit I requested some more radar airwork, specifically another attempt at acquiring some airborne targets. Sadly, the scarcity of airborne traffic in the vicinity resulted in a `non target-rich' environment. Dave selected the air-air master mode, and put the radar into B-scan search display while attempting to acquire a target. In the B-scan mode, the MFD shows an azimuth vs elevation view of the antenna field of regard. The TDC (Throttle Designator Controller) two axis control switch is used to slew the search box bars through the radar field of view. The pilot can select the velocity range within which targets are acquired and outside which they are rejected.  We acquired a target very quickly, but its altitude indicated that some hapless motorist was being painted for an AIM-7 shot! Resetting the velocities to more realistic numbers yielded little success. A bad afternoon for BVR practice.  At my request, Dave selected the AIM-7 Sparrow HUD mode, AIM-120 AMRAAM being absent in this software load. This presented a circle on the HUD and left MFD, with a range arc and supporting data.  Much to my disappointment, uncooperative afternoon air traffic denied me the opportunity to play BVR shooter! I looked forward to the possible opportunity to practice a BVR engagement against a fat juicy RPT heavy out of Tullamarine, alas I was unlucky.  I slowed to 250 KIAS and ducked under the 2,500 ft CTA step to position for an oblique downwind join, while Dave made the radio calls and demonstrated an air-air track with AIM-9 selected, against an aircraft in the Avalon circuit.    `The most notable visual differences from the `classic' Hornet are the enlarged strakes, designed to improve high AoA handling, and the edge aligned inlets, designed to improve high AoA behaviour, reduce RCS and provide increased massflow for growth engines (Photo Neville Dawson).'    2.6 In the Circuit I joined the circuit on an oblique late and very wide downwind for runway 18, pulling back the power to slow down through 200 KIAS down to about 150 KIAS at 1,500 ft and turning into a very wide base for a long final. The aim was to get plenty of time to set up for the proper glideslope. Dave lowered the gear and flaps, as only emergency gear deployment controls are present in the aft cockpit. There was no perceptible pitching during undercarriage deployment.  Dirty, with flap deployed, at 125-130 KIAS the aircraft is very smooth and stable and exceptionally easy to point very precisely. The HUD mode for landing has a very nice extended synthetic horizon line, and a glideslope vector marker as well as the velocity vector symbol. Dave trimmed the aircraft properly.  My power adjustments were producing an excessive sink rate entering finals, and on Dave's instructions I added power to get back on the glideslope. With a light crosswind from the east, very little rudder was required to get the few degrees of crab angle for a good centreline on finals. With the forward cockpit ejection seat blocking my view, the bulging sides of the canopy provided enough forward view to lean sideways and keep the aircraft comfortably on the centreline. With HUD symbology on the left MFD, the glideslope pipper is easily tracked to verify whether the descent is above or below the required glideslope.  As we crossed the threshold I began to raise the nose slightly to flare and was promptly told to `drive it in' - we hit the runway at a nominal sink rate of around 10 ft/sec, all of which was absorbed by the sturdy naval undercarriage. The aircraft swayed about 5 degrees in a slight rolling motion but within a couple of seconds righted itself as we rolled along 18. Rolling along the runway, Dave instructed me to apply a little right and then left rudder input to try out the nosewheel steering, which is quite firm. With about half of the runway gone, Dave applied mil power and on his call I gently rotated the aircraft off the runway.  We climbed up to about 1,500 ft in the circuit, and turned smoothly on to downwind. The second circuit was considerably tighter, a large pelican sighted at our altitude during the turn to final thankfully did not require an evasive manoeuvre to avoid. Again, the aircraft's smooth and stable handling in landing configuration made the circuit easy to fly precisely. Another no-flare touchdown, upon which Dave took the controls, applied mil power, rotated and then accelerated along the runway to sharply pull up in a 40 degree climb at 125 KIAS. As the aircraft hit 1,000 ft, Dave rolled the aircraft on its wingtip and flew a very tight join on downwind for a very tight circuit and descent on to finals for a showpiece landing. We stopped at about one third runway length, where I was given a demonstration of the carrier optimised nosewheel steering. The aircraft swung around almost on the spot to point downwind for a backtracking taxi to the parking area.  The flight was over, and in minutes I would have to part with an aircraft which was a sheer pleasure to fly, even at the very edge of the envelope. We taxied back with 1.1 hrs elapsed and 4,000 lb of fuel remaining.    2.7 Observations The Super Hornet is a fighter with exceptional handling qualities, even by modern fighter standards, which even a novice can handle comfortably and with confidence at the edge of the low speed manoeuvre envelope.  The point which Boeing and the US Navy have made most convincingly, is that the aircraft's flight control software is so robust that even a beginner on the type can fly it without embarrassing himself too badly. Sceptics should note that test pilot comments about fighters with this generation of flight controls being `as easy to fly as a Cessna 172' are indeed correct. There is no room for argument here, as I had the opportunity to observe first hand!  In the hands of an experienced combat pilot, such flight control software means that the pilot can be wholly focussed on the furball in progress, and need not devote any thought to pushing the aircraft past the edge into a uncontrolled departure and resulting risk of a ground impact or successful enemy missile shot. The importance of a substantially departure resistant aircraft, especially if encumbered with stores, cannot be understated - carefree handling translates directly into combat effectiveness.  In a low speed post-merge manoeuvring fight, with a high off-boresight 4th generation missile and Helmet Mounted Display, the Super Hornet will be a very difficult opponent for any current Russian fighter, even the Su-27/30. The analogue and early generation digital flight controls with hard-wired or hard-coded AoA limiters used in the Russian aircraft are a generation behind the Super Hornet and a much more experienced pilot will be required for the Russian types to match the ease with which the Super Hornet handles high alpha flight regimes.  The reports emanating from carrier landing trials performed in the US cannot be disputed, the aircraft is a sheer delight in the circuit and will take much of the anxiety out of night and bad weather traps, especially for `nugget' fighter-attack pilots.  The cockpit ergonomics build upon two decades of Hornet experience, and make for a very comfortable and easy to use cockpit environment. Again, a novice pilot will find the MFD modes easy to navigate and easy to follow. The colour moving map display makes navigational orientation ridiculously easy, against the mental chores of VOR/DME/TACAN, radar mapping and INS/map-on-the-knee navigation. The prospect of MIDS/RWR/radar/IFF tracks being overlayed on the moving map will take much effort out of maintaining wider area situational awareness.  The radar is very easy to use in MMTI, GMTI and SAR spot mapping modes, and provides an excellent tool for highly accurate all weather maritime strike, littoral strike and battlefield interdiction operations. In particular, the ability to interleave MTI and surface mapping modes is exceptionally useful for resolving and identifying moving surface targets of opportunity.  In conclusion, the reports of the Hornet's exceptional high alpha handling characteristics are provably correct. Established Hornet users should not be disappointed by this aircraft!  `The F/A-18E/F was designed for further growth, current planning includes a second generation AN/APG-79 active phased array, and funding is being sought for a growth engine based upon F-22/JSF core technology, which may also incorporate a TVC nozzle (Photo Perttu Karivalo).'    3 Acknowledgements Thanks to Boeing and the US Navy F/A-18E/F Program Office for their efforts in enabling the author to fly the F/A-18F, and especially Boeing's F/A-18E/F Chief Experimental Test Pilot Dave Desmond.

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