About the Author

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Southport, Manitoba, Canada
Steve Pomroy is a professional flight instructor and aviation writer. He has been teaching since 1995 and holds an Airline Transport Pilot License, Class 1 Instructor and Aerobatic Instructor Ratings, military QFI, and an undergraduate degree in Mechanical Engineering. He's written and published three flight training books through his company, SkyWriters Publishing, and has several other books under development. Steve currently teaches RCAF pilot candidates on their Primary Flight Training course.

Friday, May 27, 2011

Flying on Grass

Ahem... I mean... Taking off and landing on grass runways!

Get ready for spring flying! For some of you more fortunate souls, it's been spring for a while. Here in the South of Manitoba, it was winter until faily recently, then it was flood season. Now we're into spring, and the grass runways (at least some of them!) are probably dry enough to start using.

I'm a big fan of operating off-pavement. It adds another element of complexity to flight operations and makes things that much more interesting—not to mention the fact that it opens up a whole host of new destinations to visit.

But before just bombing in to a grass (or gravel!) field, there are some facts, factors, and pointers to think about. I won't talk specific techniques here, since they can vary quite a bit from one aircraft type to the next—thanks to design variations such as tricycle gear v. taildragger, or conventional tail v. T-tail. But the techniques used generally stem from one of the following points:

Keep the Nosewheel Light
If you're flying a tricycle gear aircraft, remember that the nosegear can dig-in and cause problems for a variety of reasons (e.g. – it's smaller than the main gear wheels). If the nosegear digs in, we can see performance problems (more drag), handling problems (drag at the front of the aircraft = directional instability = possible ground loop), and/or structural problems (i.e. - snapping off the nose gear!). How do we avoid all of this? remove weight from the nose gear as early as possible in the takeoff roll, and keep the weight off the nose gear as long as possible in the landing roll.

Liftoff early, but Don't Climb: Accelerate in Ground Effect
Lifting off early (i.e. - at a reduced airspeed) reduces rolling friction later in the takeoff process, reduces structural loads on the landing gear, and reduces controllability problems introduced by the soft surface. But there's a catch. Liftoff speeds used for "normal" takeoffs are determined according to the stall speed. In other words, liftoff too slowly, and you risk stalling and gracelessly falling back to Earth. This is where ground effect comes into play. Our stall speed is reduced in ground effect. So we can take advantage of this reduced stall speed to get airborne earlier. We can then also take advantage of the reduced drag in ground effect to accelerate to a safe climb speed.

Remember: You'll see Longer Takeoffs AND Landings
This one catches new pilot off guard and is a little counter-intuitive. There is more rolling friction due to the grass and soft under-grass surface. So we expect to see a longer takeoff roll. However, new initiates to grass fields also often expect to see a shorter landing roll due to the same rolling friction. But there's a catch. During landing, we can use brakes. Our brakes work really well on pavement, but not so well on grass. So although we gain rolling friction, we loss braking effectiveness. The net effect is a longer landing roll.

All in all, flying on grass can be fun and rewarding. So brush the rust off your skills, get a checkout from an instructor if necessary, and go try it out!

Happy Flying!


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