AOPA ASI Blog: Leading Edge

Wake turbulence is one of those ever present threats that we’re all aware of but much too savvy to get caught up in. The most recent incident involved a Lear 45 on approach to Mexico City that crashed several weeks ago when it go too close to the Boeing 767 it was following. The last radar hit showed just over four miles separation when five miles is considered the minimum. The cockpit voice recorder transcript dramatically showed how quickly things can go from boringly normal to completely out of control in literally seconds. There were nine fatalities on the jet and five on the ground.

I’m personally not convinced that one mile further back would make that much difference – the main thing is not to be below the lead aircraft. Back in the late 60′s and early 70′s FAA did a lot of testing on the phenomenon. The test pilot comments should be sufficient motivation to absolutely avoid the big rollers.

Danger exists not only on arrival but departure as well. I once refused takeoff clearance at Atlanta’s Hartsfield airport when ATC wanted me to follow an MD80 on climb out. The Super 80 may be a pig, according to some who fly them, but a Bonanza will not come even close to out climbing one. I had asked for an immediate turn out which ATC refused, so I refused. Since I was in holding position on 9L and royally gumming up the works, the controller suddenly became reasonable and saw things my way. No penalty, no foul, just a need to understand the physics involved.

If you fly where the big guys roil the skies remember that distance, altitude (above) and alternate flight paths are your friends.

For a quick review, take the ASF quiz on wake avoidance.

Special thanks to pilot/photographer Steve Morris for the great wake picture.

Epilogue to last week’s blog on prop safety: A student pilot was was killed last week when he hastily departed a Cessna 150 flown by another student, upon fear of being discovered of flying illegally together. Note to self: Don’t fly illegally and certainly don’t attempt exit through a spinning prop.

NTSB is just finishing a preliminary investigation on what has to be the closest call we’ve had between a GA aircraft and an airliner in years. On September 19, 2008, at 1938 local time, a runway incursion resulted in a near-collision on Runway 6 at the Lehigh Valley International Airport, Allentown, Pennsylvania. Mesa Air Shuttle flight 7138, a Canadair CRJ aborted takeoff at 120 knots skidding around a Cessna R172K that had just landed and was still taxiing on the runway. The RJ crew estimated the distance between the two aircraft at 10 feet.

Click here for an interactive recreation of the incident, provided by the FAA.

The conditions were night VMC. The Cessna had just landed on Runway 6 and the tower cleared the RJ into position and hold. Tower then discussed with the Cessna pilot where he wanted to park, and cleared him to exit the runway at A-4 taxiway. You will note from the airport taxi diagram that A-4 is the first turnoff and unless the Cessna touched down right at the end, and was moving slowly, making the first turnoff might be difficult. Some 35 seconds later, the tower, assuming the Cessna was off the runway cleared the RJ for takeoff. 23 seconds after the RJ was cleared, the Cessna pilot advised the tower that he’d missed A-4 and would like to exit on Bravo taxiway.

The skid marks speak for themselves!

There are multiple factors in this incident which both pilots and ATC should consider:

1. ATC apparently did not visually scan the runway prior to clearing the RJ and assumed the Cessna had cleared. It might also have been prudent to give the Cessna pilot more runway to get the aircraft slowed to taxi speed.
2. RJ crew apparently did not visually scan the runway prior to accepting the takeoff clearance- assumed the Cessna had cleared. It’s always good to verify that the runway is clear and if you can’t see for yourself, ask the tower.
3. The Cessna pilot should have notified the tower that he’d missed A-4 taxiway quite a bit sooner in my opinion. AIM section 4-4-1 and FAR 91.123 make it clear that you don’t have to roll it up in a ball to stop at the next taxiway if that cannot be done safely but you DO have to let the tower know, on a timely basis, that an amended clearance is needed. It would also be smart to SPEAK UP immediately if tower clears another aircraft to takeoff while you’re still on the runway.

Everyone was lucky – this time. Remember that no matter how routine something may seem, it can turn ugly faster than a speeding RJ can leapfrog a slow-clearing Cessna.

For more information on runway safety, take our Runway Safety Online Course and Runway Safety Quiz.

How do you say you’re sorry to a passenger who just walked into the prop? It happened this week at our airport when the pilot/CFI of a Cessna 172 neglected to shut down before dropping off a passenger. Our local paper, of course, put the story on top of Page One which doesn’t help GA’s image. The lady walked forward and her arm was partially severed – I probably don’t need to be any more graphic.

This happens about twice a year on average, often with a fatality, but always with serious injury. I will admit to having boarded and dropped off other pilots without a shutdown but always with a briefing beforehand. No one ever approaches or disembarks ahead of the wing – I make that absolutely clear and in retrospect, it’s probably not such a great idea. With non-pilots there is no question that the engine(s) will be shut down.

As instructors, and pilots it’s a sober reminder that the business end of the aircraft is just that and we should discuss it with those less aware. Please be mindful. Here are a few links to ASF materials on the subject.

Online course: http://flash.aopa.org/asf/engine_prop/
Safety Advisor: http://www.aopa.org/asf/publications/sa06.pdf
Real Pilot Story: http://flash.aopa.org/asf/pilotstories/prop/

This will be more than you wanted to know about the oft neglected, very reliable and very dangerous propeller. Ramp safety is just as critical as flight safety.