The H’s of Sumer Flying
I was flying for a charter company and had taken three passengers over to Hot Spring, VA one August morning in a Beechcraft Baron. As we were returning to White Plains, NY (KHPN) that afternoon I rotated at 102 kts which is 4 kts above the VMC airspeed (a/s). Ingalls Field (KHSP) has an altitude of 3,792 ft. MSL and the runway measures 5,600 ft. long.
On takeoff roll the a/c seemed somewhat slow to accelerate but I continued. After liftoff I held my airspeed and climbed out just over the approach lights. That’s when the lightbulb went ON, for me…I’m too heavy! I was caught by the Ho-Hums of summer flying:
HIGH ALTITUDE
HEAT (AIR TEMP)
HUMIDITY
The rest of the flight went very well and none of the passengers noticed what had happened. BUT I DID, and as I was clearing those approach lights the only thing I could think of is that “I owe my passengers more of a safety factor” in the future. From that experience I LEARNED…in a hurry! Let’s look at this and discuss what was happening.
The Three H’s:
High Altitude: what was the airport altitude? And what was my Pressure Altitude and Density Altitude?
Airport was 3,792’. If I had determined the PA by setting the altimeter to 29.92”hg, I would have seen the pressure altitude, which would have been higher than the airport’s elevation. This should have been my first clue.
Then correct the PA for a non-standard temperature, which was higher than the standard temp, to determine the Density Altitude.
Heat: It was definitely warm out and sitting in the terminal in the air-conditioning was also a good clue. Increased OAT decreases the air density. And again I would have now understood what to expect on takeoff and climb!
Humidity: The amount of water vapor in the air. Water vapor is lighter than air, consequently moist air is lighter than dry air. How do we determine this humidity? Look at the air temp and dew point, the higher the DP (is over about 70 degrees F) it also becomes a factor. Use the PA and then the DA Chart (Pilots Handbook of Aeronautical Knowledge, P 11-3, 11-5).
These three factors lead to a large decrease in a/c performance. The engines are not developing full thrust, the propeller(s) are not as efficient, and the airfoils are not providing as much lift. This all can lead to a bad day. My will-ism “Don’t do what I did, think about your surroundings and plan ahead.” Man, was I lucky!
Fly safe and plan ahead, file a flight plan…..Will