It seems the tendency in these things is to dwell on what happened in the flight. I don't want to do that. Instead, let me give a very quick recap. Then I want to spend some time on what I consider to be the most important things post mortem, what I learned, and what I am doing differently now.
We were flying out of Show Low Airport in east central Arizona, heading south toward town. We had been flying less than 20 minutes. I was over a heavily forested area approaching the hare balloon about a half mile ahead. I was in a 100 fpm indicated descent moving from a layer of 25-30 knot winds into 8-10 knot winds at about 400 feet AGL. I was burning to compensate for the loss of the false lift after I descended to the slower layer when I recognized a loss of pressure. I checked the tank and the needle appeared to be on full. I checked the pressure again and it was still low. I added a second tank with no resulting increase in pressure. That needle appeared to indicate full also. I attempted to shake both tanks but they were strapped in too tightly. At that point I assumed that I had a manifold problem and turned on Fire II as I continued to burn vapor. I advised my passengers that we were going to make an immediate landing. I got them positioned and gave instructions. As I was rounding at treetop level—about 70 feet—I vented to catch the treetops and slow down so I could land on a small road. The trees slowed me down more than I expected. I burned the throat and caught the back side of the envelope on a dead branch as I slipped to the ground.
The Post Mortem
Later a crew member and I recalled filling up the balloon after the previous
flight. In the meantime, however, we had a month of rain and the balloon had
been annualed. Others loaded up the balloon after the annual and unloaded it
before flight. I checked all fuel gauges the night before and they all appeared to
indicate full. I did not check them at launch time.
When I refueled after the fateful flight, I took 36 out of a possible 40 gallons. The best I can figure is that one tank was dead empty (the one I added in flight) and the other three were something just over 35%, the point at which the gauge begins to move.
During the annual, the tanks had been cinched in tighter than I normally keep them, thus making it impossible to shake them as the manufacturer recommends. I had turned loose of the Fire II valve when I positioned my passengers and was unable to relocate it in time to turn it off before I had to manage the landing. I was unable to turn off Fire II and control the vent line at the same time.
What I learned
The most surprising thing I learned was incidental to the flight. After I had
fueled and knew what had happened, I told a group of five pilots about it. Three
of the five confessed to having taken off with virtually no fuel and having to make
an immediate landing. All of the situations were different, but they all had one
thing in common: each incident had involved other people in the fueling
process.
Nothing takes the place of a proper preflight.
This seems awfully obvious, but here it is—you don't know what you forgot until it bites you.
This may seem even more obvious—if it looks like a dog, it's probably not a wolf. In other words, if it seems like my tanks are empty, it's probably not the manifold.
What I am doing differently
What I would like to see changed
I would like to see two changes made. Pilots need fuel gauges that are more
useful—that can be read easily, and that clearly differentiate between full and
empty, and the Fire II controls should be more accessible. And now I'm going to
try to think about something else.
Ed note: This story first appeared in Desert Breezes, from the Arizona Balloon Club.