To abort the takeoff or fly
Air Facts Journal

I learned to fly in Victoria, Australia in the 1960s while I studying Aeronautical Engineering at RMIT in Melbourne, specializing in Aerodynamics. I trained on Victa Airtourers at Moorabbin Airport with Civil Flying Services.  The CFI was Jock Garden a highly respected WW2 pilot, senior instructor with UK Central Flying School, and a test pilot on early jets.  The Airtourer was designed by Henry Millicer, one of my lecturers at RMIT and was built by the Victa Lawn Mower company in Bankstown, NSW.  Henry and I were of Polish extraction and we got along well.

Next to Civil was Schutt Flying School with two Mooney M20s on the flight line.  I had always been “besotted” by the Mooney as I felt the design was well ahead of the norm – it looked like it was doing 200 kts. while sitting on the ground.  I studied up on its aerodynamic design and performance characteristics as a precursor to getting an endorsement.  Coming off basic trainers, I figured that the M20 would be an exciting challenge.


Schutt Flying School had two Mooney M20s on the flight line.

The briefing was by an instructor, who was about my age, before we proceeded to the aircraft.  After a pre-flight check, we climbed on board and taxied out.  Flight control checks were good and we got our clearance.  The M20 accelerated down the runway and I had been told to look for 60-70 kts. for a smooth takeoff and climb out.  The Mooney lifted off (virtually by itself) and I could feel the acceleration.  Glancing at the airspeed indicator (ASI), I was surprised to see only about 35 – 40 kts.  The M20 was good, but surely not that good.  We continued to accelerate and had become definitely airborne but the ASI still showed around 40 kts.  Something was not right with the ASI – we were flying!!

As the remaining runway was being consumed at an alarming rate, and given that a high performance aircraft like the Mooney preferred to be airborne, I reached for the landing gear retract handle ready to “clean her up” as I fully intended to continue the takeoff and circle back to land with or without an operational ASI. As pilot-in-command, the instructor took over.  Power-off , stick forward.  Much like a flat stone skipping across a pond toward the opposite embankment, we proceeded down the runway.  To his credit, the instructor eventually managed to land on the runway, pulling up on the grass verge.  Expecting the worst, we were surprised to see that the Mooney appeared intact with no visible debris on the runway; however, the prop tips were bent back almost 90 degrees due to impact with the runway.

Many aircraft have upturned wing tips (winglets) to improve aerodynamic efficiency and reduce wing span.  Similarly, some prop blades had bent back tips to improve aerodynamic efficiency and provide better ground clearance.  These were known as Q-tips, normally done in a Jig not on a rotating engine in close proximity to the ground.  This Mooney would not be flying for some time as no doubt the engine must have been damaged.  I did end up getting my endorsement on the other M20 on the same afternoon.

What had transpired?

First, the M20 had an aerodynamically operated flap cover over the pitot tube rather than a pitot sock and flag.  At some stage, a wasp got past the flap, entered the tube, built a nest, and laid some eggs partially blocking the pitot tube causing the ASI to malfunction.

Second, the Mooney had an efficient laminar flow wing.  These are pre-disposed to a phenomenon called an aerodynamic drag bucket.  In simple terms, at low angles of attack and particular lift coefficients, the drag coefficient of the wing drops, sometimes deeply and abruptly, while the lift coefficient stays up.  The lift to drag ratio can increase markedly as you enter the drag bucket and drop as you exit.  Also, laminar boundary layers are generally sensitive to local airflow conditions and can easily “trip” into turbulence or high drag.  I believe these two aerodynamic phenomena in combination and along with the abort event, had caused our “pirouette” along the runway.  Because I had never experienced this combination, I chose to continue the takeoff.

Mooney landing

The Mooney had an efficient laminar flow wing pre-disposed to a phenomenon called an aerodynamic drag bucket.

Another factor supporting my decision was something that I experienced during my training.  My CFI had a surprise for me one day.  When I got into the Victa, I saw that he had covered the ASI. This was not in the syllabus.  Jock did help me through the initial circuits but after that, it felt natural.  I never really understood or appreciated the rationale behind this exercise but his words made some sense: “Man has always wanted to fly like a bird, so, when you fly, think and act like one, don’t you be flown”.  Maybe he wanted me to develop an “inbuilt instinct” about flying.  “You never know when”.

Lessons learned

It is almost guaranteed that the unexpected will happen quite suddenly and at the most inopportune moment and usually with little time to react.  What you do determines the outcome.  Classic advice is: stay alert, calm, think logically and resist panic.  Panic clouds judgement and reactions, usually resulting in a bad outcome.  I also think that knowing the vagaries of your aircraft helps.

Rightly or wrongly (to the casual observer), I believe, given my knowledge of the aerodynamics pertaining to this type of aircraft and prior experience during my training, I could have saved the Mooney from any damage on that day.  At no stage had I considered that continuing the takeoff would be worse than aborting.  I had every confidence I could fly the aircraft, as it was already airborne and aerodynamically stable.

The post To abort the takeoff or fly appeared first on Air Facts Journal.