Next March I had my first flights in G-VTOL, the company demonstrator.  They concerned surge performance again!  The T60 has the radar altimeter aerials mounted in a blister on the bottom of the fuselage under the cockpit and we needed to show that the wake from it did not cause disruption to the airflow into the intake at high angles of attack (AOA).  Surge boundary measurements do not need any instrumentation as the engine either surges or it doesn't at given conditions, so G-VTOL could be used to measure the surge boundaries with and without a mock-up of the blister.  Incidentally, the witness marks of the blister can still be seen on the aeroplane at Brooklands Museum today.  At altitude if you pull hard enough there will be an AOA where the engine surges.  We needed to plot the angle of attack at which the engine surged against the fan speed (rpm).  You can get to moderate AOA by just pulling on the stick (about 15 AOA) but that generally would not produce a surge at any rpm so to get to higher AOA a more dynamic procedure had to be used.  By pushing first then rapidly pulling we could get above 18 AOA using the momentum generated, we may have got close to 20 on occasions.  When the Pegasus surges it is usually just one bang with immediate recovery of the flow through the high pressure compressor.  However, about once in every ten it 'locked in', ie. the stall cell stayed in the compressor and the airflow did not recover.  With the very low airflow through the engine the Jet Pipe Temperature rose rapidly.  To avoid terminal turbine damage the engine had to be shut down within seconds.  That did not allow time for much discussion so Taylor Scott, Heinz Frick and I had very detailed pre-flight briefings so we knew exactly what we were going to do (My old friend John Lewis used to say that we will have our accidents on the ground in the briefing room before we go flying... that is the safe way).  We made the engine surge a lot in those two flights, certainly exceeding ten times and so, inevitably, we had one lock in.  It took one or two seconds to say 'It's locked in' and 'Shut Down'.  We were gliding then, descending at 6000 feet per minute so it did not take long to get below the relight boundary.  The engine relit promptly and all was well.  The auxiliary air intakes (the little flaps that surround the main intakes) were always inspected carefully after these flights as one had been blown out by the pressure wave produced by the surge and stuck once.  The surge boundaries were identical.  The radar altimeter blister had no effect.

This year Dunsfold was assembling the Hawk Mk 63 for PFTS and delivery to the United Arab Emirates.  We had to clear some new weapons for this contract and used the early production aircraft for this purpose.  The weapons included Matra Durandal anti-runway penetration weapons which we cleared for release and jettison.  I have a beautiful sequence of pictures of a full load of thirty-six (3x3 on four pylons) being released from Sea Harrier XZ440 on the range at RAE West Freugh.  The idea is to cross the runway obliquely, dropping the bombs in a ripple so that at least some of them will hit the runway.  They were released from a distance of a few hundred feet.  They have parachutes to slow them down and make them point downwards, then rocket motors to drive them into the ground before the warhead explodes.  Ours did not have warheads but it was still quite spectacular.

I made my first trips to Washington and St Louis this year.  These were busy times in the Harrier programme.  In January 1985 the first DECS trials were held at Edwards Air Force Base with AV-8B #2.  As was usual at this time of year most of the salt lake bed was too wet to use but the main paved runway was still available.  It was also quite cold.  When I arrived in Lancaster I had to negotiate piles of snow at the entrance to the Desert Inn. I could have skated on Lake Rosamund.  The team run by Bill Lowe flew 11 flights in 15 days.  Not too bad for a prototype system.  Heinz Frick had his first ride at Edwards.  Larry Walker found out that if he pumped the throttle quickly enough he could drive the rpm down by quite a margin.  I think this was again to do with the relatively low digital sampling rate and had people scratching their heads for a while but it was fixed relatively quickly.  

In March I was in Maryland again visiting the Naval Air Station Patuxent River.  This was where most of the AV-8B flying was done.  

At Dunsfold the production team was in the middle of a return-to-works programme to upgrade the Hawk TMk1 to TMk1A by adding the ability to carry and launch Sidewinder air to air missiles and carry a centre line gun pod with a 30mm Aden cannon.  We would ferry the updated aircraft to its operating base like Scampton, Chivenor or Brawdy and return with another to be modified carrying out an air test on the way.  The guys needed to practise their Instrument Landing System skills which included flying approaches and overshoots at Gatwick.  I remember one which we did at night which felt really special with an unobstructed view of the airport and the stars through the canopy.  I remember another very special day when Chris Roberts let me sit in the front seat of XX323 and fly it to Brawdy at low level past Swanage and then across the West Country and the Bristol Channel.  I did two roller landings under his close instruction before he applied the brakes in a full stop landing.  I could really see why people loved the Hawk.

The Indian Navy had bought the Sea Eagle anti-ship missile for their Sea Harriers.  One configuration carried only one missile on the port inboard pylon with a drop tank on the starboard inboard pylon to improve range.  This produced a large out of trim moment as the fuel in the tank was used so a BL755 bomb was carried on the Starboard outer pylon to partially offset the weight of the Sea Eagle.  After the Sea Eagle was fired the bomb would be jettisoned prior to landing with just the empty drop tank.  Are you with me so far?  In the case when the missile was not fired it had to be brought back to the ship as it was too expensive to throw away.  We had to show that there was sufficient aileron trim available in the hover with all the stores still attached to land safely.  There was not an instrumented Sea Harrier available at that time.  However, we could use G-VTOL with the back seat occupant being the instrumentation.  The aileron trim simply moves the stick (control column) sideways so it was very easy to measure the distance between the stick top and the side wall of the cockpit in the hover to determine how much trim movement was left.  So I found a suitable piece of string which became that very important piece of instrumentation.  After repeating the measurement a few times the experts were happy that there was enough trim left for a safe landing on the ship.  Some times you do not need to spend a fortune on instrumentation!

BAe had quite a lucrative contract with the Ministry of Defence to provide G-VTOL as a chase plane for Rolls Royce's Digital Engine Control System (DECS) development Harrier, XV277.  We took G-VTOL to Filton several times, filming XV277 tanking with a VC10 K2 and acting as a target for it to formate on.  This was to demonstrate that the DECS remained stable while being asked to perform routine tasks.  There was the economical way to get to and from Filton ie. climbing to high altitude then descending to a landing which took approximately 15 minutes.  Then there was the fun way.  I once came back at about two thousand feet.  The engine, at full throttle, was allowed to sit on the limiters (jet pipe temperature, RPM or pressure ratio, whichever it thought appropriate) all the way from take-off from Filton to entering the circuit at Dunsfold ten minutes later.  We followed the A420 road initially until we passed Chippenham then turned right avoiding the danger areas on Salisbury Plain and keeping a good lookout for gliders around Lasham.  It took twelve minutes from wheels up to touchdown to cover 120 miles, flying at Mach 0.92 or 700 miles an hour most of the way.  G-VTOL was one of the fastest Harriers Hawker Siddeley built.  The improved fineness ratio of the two seater fuselage made it marginally faster than the single seat Harrier 1 and they were both much faster than the Harrier 2.

Hawk Production Department at Dunsfold was now assembling Mk64s for Kuwait.  We had to clear more weapons for use on this Mark.  They included 540lb bombs and the gun pod where we were trialling link collection.  For the ADEN gun the ammunition cartridges are formed into a belt by links which are clipped around each cartridge and then hooked together to form a flexible belt which can be pulled from the ammunition tank and through the gun by the feed mechanism.  As they enter the breech they are unhooked and 'de linked'.  The fired cartridges are jettisoned, as were the used links.  The cartridges are relatively heavy and fly away below the aircraft but the links are very un-aerodynamic and fairly light so they 'fly' unpredictably.  In the case of the Hawk many of them would strike the ventral fins (they hit the tailplane from the Harrier).  To avoid this damage a method was devised to retain the links and collect them in a tank in the gun pod.  We had to show that there were no gun jams as a result.  The 'Brrrrrp' as the gun is fired is a nice noise!

I took part in several bomb aiming flights over the Irish Sea, refuelling at RAF Brawdy on the way back, as well as some aircraft handling trials.  We also cleared the SECAPEM target towing system.  After having filmed the deployment of the target from its container (it is a banner towed behind the aircraft on a long line) from another Hawk, Jim Hawkins demonstrated interceptions of the target from different positions.  We then monitored its clean release over the airfield.

I was not involved a lot as it was not my project, but Dunsfold was doing some preparatory work for the T-45 Goshawk programme for the US Navy (the T-45 is a development of the Hawk led by McDonnell Douglas).  Some years earlier the team had discovered that the Hawk tailplane could be made to stall in the approach configuration (with the flaps down).  This was named the 'phantom dive'.  In a conventional aircraft the centre of gravity is forward of the centre of pressure (or centre of lift).  A flying wing has moveable surfaces which bring the centres of gravity and pressure to the same point so that it is stable in pitch (up and down).  On an aircraft with a fuselage it is usual to use a tailplane to provide a downward force (negative lift) to balance the other two.  If the tailplane stalled, the aircraft would dive uncontrollably.  

The remedy was to remove the outboard foot or so of the flap vane.  The flap vane is bolted to the leading edge of the flap and guides the airflow over the flap when it is deployed for approach and landing.  By reducing the flap's effectiveness in this way the downwash over the tailplane was reduced and the stall was prevented.  The downside of this was to reduce the maximum lift that the wing would produce which would not be good for the T-45 approach to an Aircraft Carrier.  In trying to understand the phenomenon we stuck wool tufts on the underside of the tailplane of XX156 to visualise the air flow with full span vanes.  We could not fly a Hawk slowly enough to be able to chase XX156 in the approach configuration and be able to get out of the way quickly enough if/when the tailplane stalled.  The only available aircraft which could fly that slowly and remain manoeuvrable was our old friend, the Jet Provost.  We talked to a very nice man at RAF Leeming and arranged to borrow one of theirs.  Derrick Reeh from Up North picked up XM350 and flew it behind and below XX156 while I filmed the tuft behaviour.  He enjoyed a good dinner at his hotel for his trouble.  (I feel bad that we never went to Leeming to thank those guys but here is a very belated 'thank you').  

Something else had to be devised to control the flow over the tailplane so SMURFs (Side Mounted Unit Root Fins) were born.  They are small vanes attached to either side of the fuselage ahead of the tailplane which shed a vortex at high angles of attack acting a bit like the Leading Edge Root Extensions (LERX) on Harrier 2 and other high performance aircraft wings helping to keep the airflow attached and so improving lift.  SMURFs were installed on the T-45.  They had to ensure that their effectiveness was not influenced by the side mounted air brakes which were also new for that model and very close to them.

March and April 1986 saw the production DECS flying on AV-8B #2 at Edwards AFB including firing a ZUNI rocket to ensure the airflow disruption did not cause any difficulties.  Martin of Rolls Royce and Brian from Dowty & Smiths Industries Controls were there for the trials.  I was back in the UK in time for the Dunsfold Families Day.  We had one in June every year.  For some people the day was consumed by Motor Mower Racing but for many the air display was a large part of the day. The date was chosen to be the same weekend as the show at Biggin Hill and many of the participants there were happy to display at Dunsfold as well.  I think Chris Roberts and others 'liaised' quite extensively to make it a good show.  This year, as well as the 'local lads' flying a Harrier GR Mk5, two Sea Harriers and a Hawk we had the Royal Navy Historic Flight's Sea Hawk and Sea Fury, a privately owned Hunter, the Mosquito, a pair of motor gliders sponsored by Unipart and the Sharks helicopter display team among others.  The MoD aircraft were always briefed and flown on trials flights, joining up at the end of those flights for a couple of formation fly-bys.