Twin Proficiency: Three Oshkosh Topics

Twin Proficiency: Three Oshkosh Topics

EAA AirVenture is the world’s largest gathering of pilots and the aviation industry. If you have never attended, make plans for next year … and prepare to be awed by the sheer scope of the event. Not only will you be blown away by the numbers and varieties of aircraft and exhibitors, you’ll also have an unparalleled opportunity to meet pilots of all experience levels and discuss flying technique.

This year, three topics each came up multiple times in my discussions and presentations, conducted at this year’s EAA AirVenture:

First, there’s frequent discussion of managing fuel by using every drop from a tank. Running a fuel tank dry, then immediately switching to a tank containing fuel, should result in the engine continuing to run. This is a time-tested technique for getting the absolute, greatest range from an airplane. But should we be pushing our fuel so close to the limit? Is causing the engine to momentarily quit – to intentionally cause engine failure – a good idea?

If the engine would relight immediately 100% of the time, it might be. But the record shows that’s not always the case. Seemingly weekly, an off-airport landing appears to be fuel starvation, when a tank ran dry and, although fuel was available on the airplane, switching to the fueled tank wasn’t successful. A study I conducted of one airplane type shows running a tank dry is a common contributor to off-airport landings (see www.thomaspturner.net/Fuel.htm). I expect that this is common to all types of aircraft. Many pilots, however, swear by achieving maximum-range flight by running all but the last fuel tank completely dry. For those who employ this risk-management strategy, be aware that the possibility does exist that air in the fuel lines or other factors may prevent the engine from restarting after your intentional engine failure. Just because you’ve successfully used the dry-tank routine for years does not mean it can’t happen the next time.

Let’s put this discussion in the context of twin and turbine-powered airplanes. Most modern twin-engine airplanes have simpler fuel systems than many piston airplanes. And, logically, fuel starvation is unlikely to occur simultaneously to both engines in a twin – you’d expect to have time to recover from a one-engine outage before being faced with starvation in the other. However, we still read reports of fuel starvation in multi-engine airplanes when the pilot attempts to take off, maneuver in the airport traffic pattern for landing, or begin a go-around or missed approach when auxiliary fuel tanks are selected (every aircraft auxiliary tank I’ve ever seen carries a limitation against use in other than level flight). So, be sure to set and check your fuel selectors properly before takeoff and again for descent and landing, to avoid inadvertently running tanks dry (or at least unporting the fuel) at a point from where there’s no room to recover.

In a more normal, but range-extending, context, intentionally running a fuel tank dry still crops up as a piloting tactic. Pilots who advocate this strategy usually tell me they can anticipate within a few minutes when the tank will empty and the power gauges “twitch” and go dark. I respond that if the pilot can tell the tank will completely drain within, say, five minutes, that he or she should go ahead and switch away from that tank at that time…not waiting for the engine to quit and need to be restarted. I quip that if that extra five minutes’ fuel makes the difference between completing a flight and not then the pilot has larger risk management issues to work through.

Second, Oshkosh pilots talked a lot about runway excursions caused by landing short or landing long – undershooting the runway or landing and rolling off its far end.

Each of these scenarios is a symptom of airspeed and glidepath control gone bad. In many airplanes, every additional five knots on final increases the distance to flare and land by 10% or more. Even a little below final approach speed, on the other hand, causes the rate of descent to increase, angling you short of the runway.

Your final approach check should include:

  • In configuration (flaps, landing gear)
  • On speed
  • On glidepath, electronic or visual, if available, or, if not,  to a touchdown point in the first third of the runway.
  • On centerline (aligned with the runway and compensating for any crosswind)

If you’re within 200 feet of the ground and any one of these items is not as it should be, smoothly execute a go-around and set up the aircraft to try again. Make a conscious decision to include a check of these items on final approach or when breaking out from an instrument approach to near minimums. Don’t try to “salvage” the landing at the last few seconds or that’s exactly what may happen to your airplane.

Third, a related topic, is the great number of stall-related crashes in general aviation airplanes. The FAA, NTSB and industry has made much of the Loss of Control – In Flight (LOC-I) record, which is implicated in about 80% of all fatal aircraft crashes. Most LOC-I events are aerodynamic stalls, so a lot of discussion – at Oshkosh and throughout the industry – centers on angle of attack indicators and other stall-avoidance technology. In fact, EAA presented its first-ever Founder’s Innovation Prize this year at AirVenture, in a contest that specifically called for technological solutions to reducing the stall/spin accident rate.

Aviation safety advocate Fred Scott makes an interesting observation about LOC-I: stall/spin crashes happen not because pilots fly their airplanes too slowly, they occur because pilots don’t fly their airplanes slowly often enough. Specifically, Fred suggests the modern practice of flying long, wide traffic patterns, coupled with flying at fairly high pattern speeds and power settings, conspires against pilots when, for some reason, conditions require them to fly more slowly. For example, a close-in pattern for spacing or a high density altitude takeoff with a loaded cabin can be easily and safely flown (assuming you’re within airplane limits), but to do so you must be comfortable with the visual and tactile cues and the small turning radius at these slower speeds.

If you haven’t practiced flying (appropriately) slowly while close to the ground, these scenarios will be unfamiliar to you. You might not fly airspeeds and power settings as precisely as you should; you may not correctly respond to visual cues to practice the proper “flight path management” that is a new buzzword in aviation safety circles. With or without angle of attack indicators or other new cockpit technologies, stall avoidance requires you to be practiced in precision flying and compensation for unusual sensations that you’ll only detect as being abnormal if you’re very familiar with what “normal” looks and feels like.

Oshkosh presents a unique opportunity to speak informally with a wide variety of pilots to find common areas of concern and discern techniques to make your flying more precise. Take advantage of every chance you get to learn from others’ experience, and to help others learn from yours.

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