Helicopter Lift Theory – Equal Transit, Skipping Stone & 1/2 a Venturi – all wrong…
Asked by: J
OK so here is a frustrating situation for a new Helicopter CFI working on how to teach lift theory:
The 2012 FAA Helicopter Flying Handbook explains the creation of lift as a combination of half a venturi (the bottom half is the airfoil) and air pushing up on the bottom of the airfoil (like a water skier).
The 2012 FAA Helicopter Instructor's Handbook explains lift as the upper surface having a longer distance for the air molecules to travel than the lower surface and so causing the airflow above to speed up to make sure the molecules meet at the trailing edge.
Two different theories in books released within a month or two of each other!!! To make things even more frustrating, both explanations are completely wrong according to NASA:
So apart from a moan at the FAA, the question is what do you teach a new helicopter student:
- What the Helicopter Instructor's Handbook says you should teach - 'Equal Transit Time' theory
- What the Helicopter Flying Handbook teaches - a combination of 'Skipping Stone' & '1/2 a Venturi' theories
- What NASA (who put a man on the moon using a pocket calculator) says - ' Turning of a fluid'
I WANT to teach option 3, but will they suffer in written tests and at the hands of DPEs because of it?
Note to the FAA - the NASA theory has been established for a long time - even longer than the amount of time ADFs have NOT been used in the cockpit... ;-)