Nalls Aviation - Home of the Sea Harrier

Normally, 13 would be an unlucky number.  However, in this instance there is ONLY good news to report.  As you might recall, our last Update was the bearer of bad news- our Gas Turbine Starter (GTS) decided to self-destruct on start.  After a close examination, the cause was determined to be an improperly peened bolt head, which secured a mounting bracket for a main bearing inside the GTS. The bolt could rotate, allowing the mounting to loosen. This further allowed the bearing to move ever so slightly, which was just enough to lead to destruction.  The power turbine contacted the turbine nozzle at 80,000 RPM.   Shortly after, the turbine failed and the rest is evident.  At 80,000 RPM is doesn’t much matter which failed first – the bearing or the turbine, the end result is the same.  Because of the improperly peened bolt, failure would occurred eventually, whether on this particular start or sometime later.

In the meantime, we now have three good GTS’s and our own ground run test stand.  We can’t duplicate all the tests of the factory, but enough to test run a starter and be confident enough to install one on the airplane.  These little starters are pretty amazing.  They are the size of a large coffee can and actually a small, jet engine.  They turn at approximately 80,000 rpm and produce 87 horsepower.   From that, we extract enough electrical power to run the aircraft systems on the ground and to start the Pegasus engine.  Two of our new ones came from the UK, and one was salvaged from a go-kart in the mid west.  Another one was purchased on Ebay and we should be able to use it for training or spare parts.  We are not the only customers looking for exciting things to do with 87 horsepower from a small engine.  Have you seen the jet-powered outhouse at airshows?  That’s what I’m competing against…..

We installed a good starter and have completed all our ground run checks.  The electrical system is now working perfectly, the pitot / static system has been completed, checked, and certified, the transponder has been checked and certified, and we have taxied the airplane several times.

The engine is a real screamer.  The test cell run sheet indicates that it produced 21,600lb thrust on the cell.   Our basic airplane weighs 13,600 pounds empty.  Even with a full internal fuel load of 5,000 pounds, we have a gross weight of 18,600 lbs.  On our very first takeoff, we will have a thrust-to-weight greater than one!

The top-end engine RPM’s are perfect, as are the acceleration times.  For those of you who have never experienced a Pegasus engine, it’s nothing short of astounding.  Pick whatever adjective you want, there are no words - - not even spiced with profanity - -  to adequately describe the feeling of acceleration from a Pegasus and a light-weight Harrier!

Prior to each takeoff, the pilot times, with a stopwatch, the low-end engine acceleration  from 27 to 55% RPM.  Fifty-five percent is the maximum RPM this airplane can sustain on the ground with the nozzles aft and have the brakes still hold the plane in position.  Beyond that RPM, the airplane will skid forward - - brakes or no brakes.   There have been shipboard takeoffs with the brakes fully locked and there was little, if any, difference in end speed.  There were two blown main tires, but no difference in end speed.

Assuming that time is within limits, the pilot completes his takeoff checks and slams full power.  The engine then accelerates from 55% to the top-end RPM (103.8% dry) in less than 3 seconds.  In those 2-point-something seconds, the airplane literally jumps forward and is at flying speed nearly as soon as the pilot’s throttle hand reaches full throw.

To the uninitiated, this may seem an exaggeration, but I assure you it’s absolutely truthful.  I don’t believe there’s any airplane in the world, even to this day, that has the acceleration of a light-weight AV-8A Harrier or the Sea Harrier. The acceleration even astonished the ground crew.

This airplane will accelerate to flying speed in only a few hundred feet.  We use 300 as the minimum takeoff distance on the ship, without a catapult, because the pilot cannot physically get his hand from the throttle to the nozzle lever any quicker in a shorter distance.  I have not felt this acceleration in some time, and a simulator is inadequate for this.  It took a couple of trips up and down the runway to become accustomed to the Pegasus again.  Any Harrier pilot can attest to how fast this little rocket can be!

Oh, I forgot to mention that to time the accelerations for the top-end RPM, my left hand is on the throttle and my right hand on the stopwatch, located on the upper right instrument panel.  I don’t have a third hand to control the stick – which further adds to the excitement.  It had been a while since I had done this, as well.

After I was convinced the engine and systems were operating completely normally, and had become accustomed to the airplane again, the temptation was there to just take it for a spin around the patch.  But, we’ll get there in due time.  The engine is perfect, the systems are perfect and signed off, the weight and balance has been double-checked and within limits, and we’re nearly ready to go.

Our last ground runs also confirmed that we can operate completely safely from our civilian airfield, St. Mary’s County.  We originally planned to use NAS Patuxent River for the first flight.  However, our request was denied.  The civilian airfield is 1,000 feet longer than an auxiliary airfield used routinely by the Marines in North Carolina and will be more than sufficient.  Our recent taxi checks allowed me to accelerate to flying speed, stop, accelerate again to flying speed, stop and repeat that all a third time within a single runway length.  We will have no problem operating from this airfield at all.  Our only outstanding discrepancy remaining is a fuel leak, which is being repaired.  We will also certify and install a “hot” ejection seat.  After that, we’re ready to roll.

As it turns out, the GTS failure was a blessing in disguise, but it did set up back two months.  We now a number of spares, plus manuals, as well as a source for parts.  We also have a couple of new team members who have come forward to help us.  We can always use more help and advice and the enthusiasm continues to build as we near a launch date.  With each day, we move closer to our first flight and have more and more confidence that we’re doing this right - - one step at a time.