Or why I won’t do aerial photo/video flights with three passengers on board.
It’s that time of the season again: time to go through the NTSB reports to see how and why helicopters are crashing. As I’ve mentioned elsewhere in this blog, it’s usually due to “stupid pilot tricks.” Here’s yet another example.
The full narrative is a bit lengthy to quote here, but I’ll summarize:
R44 Raven I helicopter with four people on board. The pilot estimates the weight of the aircraft at the time of the accident was 2,391 pounds — just 9 pounds less than max gross weight for that aircraft. The accident occurred 25 to 30 minutes after takeoff. If the aircraft burns 15 gallons per hour (as conservatively estimated by Robinson), it burned at least 7 gallons during the flight. 7 gallons x 6 pounds per gallon = 42 pounds. So yes, the helicopter was over max gross weight at takeoff. No wonder the pilot “was concerned with the density altitude at the departure airport.”
Speaking of density altitude, the temperature was 31°C at the closest weather station, which was 12 miles away and sat at 4,964 feet. The calculated density altitude was 7,721 feet. The wind was 17G32.
The purpose of the flight was aerial photography. As any commercial pilot can tell you, that often means low and slow flights. So slow, perhaps, that the helicopter began to settle (under power) during a turn about 100 feet above the ground. There was a close call with two sets of power lines, which the pilot was able to clear while the low rotor horn blared. But the pilot was unable to gain enough speed and keep enough altitude to prevent settling into the ground. The helicopter rolled and three of the four occupants received minor injuries. The helicopter was totaled.
A look at the performance chart for an R44 (Raven I) makes it pretty clear why the pilot had trouble maintaining altitude at slow speed. At max gross weight on a 30°C day, the helicopter can’t even perform an out of ground effect (OGE) hover at sea level, let alone nearly 5,000 feet. That means it would have to continuously fly above ETL (approximately 25 knots airspeed) to stay in the air. At slow speed, a turn into a tailwind situation would rob the aircraft of airspeed, making it impossible (per the performance data, anyway) to stay airborne.
(It’s important to note that the R44 Raven II helicopter has much better performance at high density altitude. That’s why I paid the extra $40K to buy a Raven II instead of a Raven I.)
How could this accident have been prevented? Lighten up the aircraft. One way is to take just the passenger with the camera. Leaving two passengers behind would likely have lightened up the aircraft by 300 (or more) pounds. According to the OGE hover chart, at 2,050 pounds, the helicopter could (barely) hover out of ground effect. But even in that situation, the high density altitude would have made the helicopter sluggish and limited its performance. While an experienced pilot may have been able to pull it off, not every pilot could.
But this doesn’t excuse the pilot from doing his homework. A quick look in the pilot operating handbook (POH) would clearly show the aircraft’s limitations. The chart is in there for a reason.
Still, I could put myself in the pilot’s shoes and envision his situation. He knows density altitude could be an issue. But there are three guys and they see a helicopter with three empty seats. Why can’t they all fly? The pilot does a test flight with two of them on board and doesn’t have any trouble. What’s one more person, the passengers ask. Joey really wanted to come, too. The pilot succumbs to the pressure of this passengers and does something he knows deep down inside is probably very stupid.
And he pays for it.
How many times has this happened to you? Once?Twice? Ten times? I know that some version of this has happened to me. Every time it’s happened, I walked away without any problems. But during the whole flight, I worried. I knew what could happen. And I was relieved when things didn’t go wrong.
Is that the way we should be flying?
Now I personally have a hard and steadfast rule: maximum of two passengers for aerial photo/video flights — preferably just one. And if I don’t feel like I have enough reserve power under the flying conditions — keeping the OGE Hover Chart in mind — I won’t do any hovering or very slow flight.
In my opinion, it’s not worth risking the safety of flight just to make a client happy.
Think about this the next time you’re preparing for an aerial photo mission.