Engine Failure at 10,500 ft With Terrain Below and Two Bad Options
You are cruising a normally aspirated single at 10,500 ft MSL over rising terrain. Best glide is 80 KIAS; you determine that at best glide the airplane descends at 800 fpm with a true airspeed of 96 kt. The wind at your altitude is a direct headwind of 20 kt. The engine begins to run rough, then quits; the propeller is windmilling. Terrain in every direction is 3,500 ft MSL. An airport with a 2,600-ft paved runway lies 9 nm ahead. A 1,900-ft grass strip lies 3 nm to your left, and a flat plowed field lies about 1.5 nm to your right. You need about 1,000 ft of altitude to maneuver in the pattern.
1. Compute the no-wind and the actual headwind glide distance available, and state whether the airport is reachable.
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Usable altitude: 10,500 - 3,500 (terrain) - 1,000 (pattern margin) = 6,000 ft.
Still air: sink 800 fpm at 96 kt TAS. Time to lose 6,000 ft = 6,000 / 800 = 7.5 min. Distance = 96 kt x 7.5/60 = 12 nm.
With the 20-kt headwind: ground speed = 96 - 20 = 76 kt. Distance = 76 x 7.5/60 = 9.5 nm.
So on paper the airport at 9 nm is just reachable - by half a mile, about 24 seconds, a few hundred feet.
Now subtract the real-world debits: the 10-15 seconds before you recognized the failure and established best glide (about 0.3 nm), the trim and configuration changes, any turn onto the airport heading, and the fact that a windmilling propeller gives a worse glide than the clean figure - typically 150-250 fpm more sink until it is slowed or stopped. Any one of those erases the margin, and a 10-kt increase in headwind erases it outright.
The honest conclusion: the airport is not a plan, it is a hope. You should turn toward it only if you are willing to abandon it, at a pre-briefed altitude, for the field.
2. What is your decision framework between the airport, the grass strip, and the plowed field?
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Decide by elimination, working from the certainty of the outcome:
Airport (9 nm, paved, 2,600 ft): best outcome if made, but the glide computation leaves essentially nothing, and you arrive at the pattern with no altitude to maneuver - meaning you must hit the runway from a straight-in with zero correction capability. Committing to it removes your ability to change your mind later, because it lies at the edge of the glide cone.
Grass strip (3 nm, 1,900 ft): well inside the glide envelope (you would arrive with roughly 4,000 ft of altitude to spare, plenty for a pattern and a high key position). A 1,900-ft grass strip at best-glide ground speed of about 76 kt is short and the rollout is soft, but it is a prepared surface of known length, usually with clear approaches, and it is 3 nm of solid glide away rather than 9. On balance, this is the strong favorite.
Plowed field (1.5 nm): the guaranteed-damage option. Plowed ground will stop the airplane in a very short distance and will probably tear off the gear and possibly flip it. Reserve it for when nothing else works, and pick it now, while you still have altitude to maneuver, rather than after the alternatives have failed.
Framework: select the strip now, fly best glide toward it, keep the field as your alternate at a stated altitude, and turn toward the airport only if you find yourself high on glide with margin to spare. Never trade a known-good option for an unverified one.
3. List what you would attempt before committing to the off-airport landing, and what you must accomplish with the radio.
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Attempts (brief, time-boxed, without abandoning the glide):
- Fuel selector to the other tank, and confirm the valve is not in an intermediate position; mixture rich; carburetor heat on (ice is a real cause at this altitude and temperature); throttle forward; boost pump on if the airplane has one.
- Magneto check and, if applicable, cycle the ignition switch.
- Establish best glide and trim immediately - this is the first action, before any troubleshooting, because altitude is the only currency you have.
- Once it is clear the engine will not restart, secure it: mixture idle cutoff, fuel off, ignition off, and slow the propeller if the airplane allows it, to reduce drag and extend the glide.
Radio:
- Declare an emergency on 121.5 if you have not reached anyone, or on the current ATC frequency; state position, altitude, intentions, and souls on board.
- Squawk 7700 if a transponder is available.
- Set the transponder to the emergency code before the descent takes you below radar coverage, and attempt one transmission to a nearby facility or another aircraft.
- Brief passengers on the forced landing, and secure the cabin before short final.
The discipline is that troubleshooting never displaces flying the airplane - and once you have selected a landing area, the landing itself gets your full attention.