Density altitude has a significant impact on your aircraft's performance. Even turbocharged aircraft can struggle to perform on high density altitude days, like this Cessna 182...
The Accident Go-Around At Lake Tahoe Airport
The pilot reported that during landing the airplane floated half way down the runway, so they decided to perform a go-around. During the go-around, the pilot reported that the airplane would not climb initially and one wheel touched down on the runway, which "threw the airplane off kilter." Subsequently, the airplane did start to climb, but the flight path was over the grass to the right of the runway, so they forced the airplane down in the grass ahead. During the touchdown, the nose gear collapsed and the airplane nosed over.
During a postaccident interview with the National Transportation Safety Board investigator-in-charge, the pilot reported that during the go-around, they retracted the flaps to 20 degrees, but they forgot to remove the carburetor heat because they normally fly fuel-injected airplanes.
The fuselage, both wings, and vertical stabilizer sustained substantial damage.
The pilot reported no preaccident mechanical malfunctions or failures with the airplane that would have precluded normal operation.
The Normal Go-Around Procedure
The pilot's operating handbook for the airplane states that:
For a Balked Landing
- 1. Power - FULL THROTTLE and 2400 RPM [revolutions per minute].
- 2. Carburetor Heat - COLD.
- 3. Wing Flaps - RETRACT to 20 degrees.
- 4. Climb Speed - 75 KIAS [knots indicated airspeed].
- 5. Wing Flaps - RETRACT slowly after reach 75 KIAS.
- 6. Cowl Flaps - OPEN.
Weather At The Time Of The Accident
Around the time of the accident, the automated weather observing system reported the winds variable at 6 knots, a temperature of 66 degrees Fahrenheit (19 Celsius), and a dew point of 26 degrees Fahrenheit (-3 Celsius). The airport's elevation was 6,268 feet above mean sea level (MSL) and the density altitude was 8,108 feet above MSL.
66 degrees Fahrenheit (19 C) really isn't that warm, but at 6,268 field elevation it is. ISA is 15 degrees C at sea level, but it decreases approximately 2 degrees C per 1,000 feet. At field elevation for KTVL, the ISA temperature is only 2.5 degrees C. That means during the go around, the airport conditions were ISA +16.5 degrees C, which has a significant impact on aircraft performance.
In fact, according to the aircraft's POH, takeoff distance over a 50 foot obstacle with the weather at the airport was nearly 1,000 feet longer than it would have been at sea level on an ISA day. And that doesn't take into account the carb heat that was left on...
Knowing Your Aircraft, And The Procedures That Go With It
It's likely the aircraft had enough performance to go-around, but when the carb heat was left on, the engine simply wasn't able to produce enough power.
Carb heat routes warm air, usually from the exhaust shroud, into the carburetor. And while that warm air is great at melting ice, it also reduces your engine's power output.
That's because warm air is less dense than cold air. When you draw less dense air into your engine, you get less performance as a result, usually to the tune of several hundred RPM less.
The pilot stated in the report that they normally fly fuel injected aircraft, and they forgot to turn carb heat off during the go-around. It's a mistake any of us could make, especially in an unfamiliar aircraft, during a demanding maneuver.
How Familiar Are You With Your Plane?
If you had an abnormal situation like this on your next flight, how well do you think you'd perform?
Most professional pilots are required to go through recurrent training every six to 12 months. And in that training, they go through just about every abnormal and emergency situation imaginable. After reviewing systems and procedures in ground school, and practicing in the sim, they head back to the flight line, refreshed on every procedure in the book.
The same isn't true for GA pilots. We're only required to pass a flight review every 2 years. The minimum required training time for the flight review is 1 hour of ground instruction, and 1 hour of flight time. And getting a checkout in a new aircraft type usually only takes a few hours to complete, despite an entirely new set of checklists and limitations that the aircraft brings with it.
If something goes wrong on a hot summer day, your margin for error can be very narrow.
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