It was a hot, sweltering summer day in Las Vegas. Las Vegas, New Mexico that is.
Running a little low on fuel, our pilot decided to make a quick stop at the Las Vegas Municipal Airport. There’s not really much to do but get fuel at KLVS, so the stop was quick and the tanks were full in about 15 minutes.
Our pilot had spent all Spring operating in the Mid-Western United States, mainly in temperatures around 80 degrees. His trusty Cessna 172P had proven itself capable of carrying him and his cargo anywhere he desired.
Today the temperature was around 90 degrees, and KLVS sits at 6,877 ft above sea level. Nothing on the approach had indicated any issues, and the wind was favorable for Runway 14 which is over 8000 feet long, which is plenty for a small Cessna.
Our pilot taxied out to the runway and started the takeoff roll. As the aircraft reached about halfway down the runway, he noticed that his airspeed was still nowhere near takeoff speed. He made a small note, but elected to continue the takeoff roll anyway, figuring it was just a few seconds until he was airborne.
With about 1000 feet of runway remaining, the 172 leapt into the air and started a slow climb. Slow in this case was about 25-50 feet-per-minute.
And then they came into view. In the gently up-sloping pasture ahead was a herd of hundreds of cattle, grazing the country side.
“Oh, my god, I’m going to hit a cow…”
It was right about then our pilot remembered a small piece at the end of the ASOS which stated the density altitude was 10,500 feet. Combined with the aircraft being at near gross weight, the pilot started to put it all together.
He leaned out the mixture a little bit, got a little more power and just skipped over the cows, missing them by about 20 feet. He circled in the valley until he could climb over the mountains and on his way west.
Would you have caught the density altitude recording on the ASOS?
What was the first warning sign and what could have been done?
Could it happen again to the same person?
Do you have a direct experience with high density altitude?
This is great. I own a C172G 1966 with 0-300-D, 145 HP Not much power but I love my ship. Got my ticket in 1980 when I owned a Tri-Pacer 150. Went to rusty status for 20 + years then decided to get back into aviation buying the Cessna. Took a 6 hour bi-annual and I was signed off, where the real learning starts, when you are alone with the plane in the air. OK now you have that I will get to the point. I learned about density altitude (DA) from a 2500′ grass strip on a 95 degree day in Alabama. When I took off the plane was not getting to speed. I slowed down to a craw and turned around to start another run in the opposite direction, starting as far back as would allow. This time I made it with a bit to spare, and while climbing I noticed I was so nervous I still had the carb heat out. Duh. So when I got home I researched this thing called DA. You see when I had the Tri-Pacer I lived in Ohio and it never got that hot. But here in Alabama it stays hot all summer long, and this year was the worst. Now I carry a little app called AutoDens on my I-Phone and I-Pad that gives DA in several ways. BTW when in Ohio my buddy has a farm with his own airstrip in the cow pasture. When I used to land there I had to run the cows off the runway, then circle around and land. I did not have wheel fairings so when you hit the piles of cow manure, you always had to clean under the wing. Love your site and there is a lot of good info for this old pilot to learn. Now for a suggestion, show how to use DA in figuring out how much runway you would need. My app shows what the DA is, but not how to add that onto the length of roll needed.
When density altitude is high engine as well as wing and propeller performance drops. Decreasing the load of the plane(less baggage, only the fuel required to safely and legally complete the flight) , choosing to fly earlier in the day (before it becomes too hot) will help . It pays to read and understand the performance charts while safely on the ground and determine beforehand if flying will be possible or it’s better to cancel.