The pilot reported that, during takeoff at the airport in Las Cruces, New Mexico, with a density altitude of 6,750 feet and the airplane’s weight near gross weight, acceleration seemed sluggish.
The Liberty XL-2 lifted off about 1/3 of the way down the runway after achieving 55 knot rotation speed, but the climb was also “sluggish,” he told investigators.
The airplane cleared the airport perimeter fence and began to settle. It subsequently touched down on soft dirt and nosed over.
The airplane sustained substantial damage to both wings.
The pilot reported that there were no pre-accident mechanical malfunctions or failures with the airplane that would have precluded normal operation and he believed that the cause of the accident was a combination of high-density altitude and the airplane’s weight close to the maximum allowable gross weight.
Probable Cause: The airplane’s inability to climb during takeoff due to a degradation of engine performance due to high density altitude. Contributing to the accident was the pilot’s decision to continue the takeoff.
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This March 2022 accident report is provided by the National Transportation Safety Board. Published as an educational tool, it is intended to help pilots learn from the misfortunes of others.
This was an engine miss-management problem, not directly related to the high density altitude.
From the POH, the aircraft can climb at 300 fpm at a pressure altitude of 7,000 ft.
The pilot mentioned leaning the mixture to an EGT setting, so the engine was not the IOF-240 in the FAA registry…maybe the IO-240 listed in the 6120.
[ the IOF-240 has no mixture control with the FADEC system]
The proper thing is to lean to best power, which is max rpm….That was the pilot’s error.
Also, the POH specifies using 20 degrees of flaps for takeoff….which was not mentioned in the pilot narrative..??
I’ve flown out of Las Cruses in July with a 6,800 DA, and the C172 with a tired O-300 had no trouble climbing at 300-400 fpm, and we we near gross weight too.
The LOW density of the elements that make up the air….. primarily nitrogen and oxygen…….. NOT HIGH density………… low density, low density low density……. both the air breathing engine and the human body need oxygen……… the wing and the propeller need to move a mass (could be air, could be water, etc) ……… High, Hot and Humid will cause the supply of oxygen molecules to be less than the standard day performance datum………. BEP-W Brain, Engine, Propeller, Wing…… one needs to calculate what will be the impact of being higher than the standard datum, hotter than the standard datum and having more moisture (standard datum being sea level, 15C/59F and 1013.2 mb/29:92 in of Hg…….. take the words high-density altitude out of your vocabulary.. and concentrate on the DENSITY of what is available……… the LOW density of the stuff we need is the problem…… HHH are the drivers of how the aircraft and your brain will work… High position as compared to the sea level datum, hotter than the datum…. and humidity as a water molecule will displace any oxygen molecule.
All of us pilots know what the phrase ‘high density altitude’ means, which is that the effective altitude is higher than the field elevation.
It is a widely understood phrase.
If there is an ASOS at an airport, it will be part of the announcement, ‘density altitude xxxx feet’.
When the temp is well below the standard temp and pressure, we have ‘low density altitude’….sometimes when the temp is in the 30’s, the ASOS announces ‘density altitude, minus 500 feet’ [ my home airport ].