rondezvous with alfalfa; a cautionary tale
Posted: Tue Oct 21, 2003 9:36 pm
'During the last week of September, my wife Debra and I took our 1937 24G
from its base in south central Idaho (Gooding) to NW Oregon. The Pacific
NW was enjoying an exceptional bit of fine weather.
We had a bit of an adventure on the way back.
The weather in western Oregon went to pot although east of the Cascade
Mts it was CAVU. On Monday, the 29th, we were delayed departing
Hillsboro, OR, (just west of Portland) until 3pm because low clouds
barred us from crossing the 1300 foot hills between the airport and the
Columbia river. We finally got out around 3 pm and slipped under the
scud over Vancouver, WA and then out the Columbia Gorge. We left with
our two 30 gallon tanks topped, and flew 3 hrs east to Joseph, OR. Six
deer were quietly grazing next to the runway as we whizzed by. They
stayed put.
There is good camping on the airstrip at Joseph and its an easy walk in
to town for great food. Good thing we were doing a bunch of walking.
The next day we left at noon for what I anticipated would be a 2 1/2 hr
flight back to Gooding. My dipsticks indicated four hrs of fuel on
board. We hit stiff winds headwinds (unusual when flying west to east)
and at 2.5 hrs were still 40 minutes to Gooding. As I overflew Mountain
Home, where I could have picked up fuel, I checked my fuel figures and
pressed on.
At three hrs the engine quit. No sweat, I think. I was expecting the
right tank to be low. I switched to the left tank and the engine surged
to life. And quit again. And surged. And quit.
I looked at Deb and told her I guess we were landing, so cinch up tight.
We were only
about 1500 ft above ground, so we didn't have a lot of time. A large
irrigated field was just behind us, rough sage and lava lands everywhere
else.
The field was an alfalfa field, and the hay had been taken in recently.
The northern half of the field was littered with hay bales and crossed
by a power transmission line. The southern half was partially being
irrigated by two parallel hand lines running east-west. I picked a path
parallel them between the sprinklers and the southern field edge. I got
off one brief mayday on 122.8.
On short final I realized there was a line of wooden utility poles
angling across my path. The choice was over or under; under seemed the
surer bet. While crossing
under the right wing struck one wire about 4 feet from the wingtip....
but the wire broke away--whew. (I later discovered the land angled down
sharply from left to right; the lowest point of the wires was not
centered between the poles. I was very lucky.)
I completed the landing and got us stopped before the end of the field.
I called Chip Gibson, my mechanic in Gooding, which was only 20 miles
away, and he came to the rescue with 10 gallons of gas. We offloaded our
gear and I flew the plane out of the field, while Deb rode to Gooding
with Chip. (Cell phones are handy; I had a chat with FSS and the FAA
while I was waiting for Chip. My mayday had been reported.)
How did I end up an hour short on gas?
I was't, actually. We found 2.5 gallons remaining in the left tank. This
was less than the 6 gallons I assumed were there, but it was enough to
get us (just) to Gooding.
I now think I understand the warning placed on my fuel valves (caution:
run on only one tank at a time) This warning was required by an
Airworthiness Directive that very tersely states:
To eliminate the possibility of engine failure due to air-lock in
the fuel system, the fuel tank selector valve should be placarded
immediately to specify that fuel be fed from only one tank at a time.
I had assumed this "air-lock" was referring to vacuum build-up in the
tank. I(and the GADO) now believe it is a quirk of the fuel system; if the
line from a tank to the carb ever runs dry the second tank will not feed
unless the first is closed off. The arrangement is gravity fed; two
lines from the tank meet at a common point (think Y) with a valve at
each tank. Without a good head of fuel, the engine just keeps sucking
air even if the valve on the tank with fuel is opened. I hadn't
immediately closed the right tank when the engine quit. I opened the
left, then got really busy.
[I got the vacuum idea from a note written in July, 1994, from C. Mack
Gavitt (the owner who financed the rebuild of N2088 in 1992-1993, to
Blake Henderson, the owner I purchased N2088 from.
"Be careful with the fuel caps. It vents thru the caps.
I'd burn one hr., Switch tanks, burn 1 hr. Repeat and then -- on
the third burn - time it until the engine burped. The theory being
that you now know how much time you have remaining. Don't use this
method. I was on short final to an Iowa corn patch when it came back to
life. Fairchild's are famous for fuel starvation problems . Check the
caps every time."
It now seems clear to me that Mack was experiencing the same type of
air-lock I encountered, a lack of flow due to insufficient head in the
tank and air flow from the empty tank.]
This explained, where did the rest of the missing fuel go? Well,I had
calibrated my dipsticks "top down"; that is, by measuring how much fuel
it took to get from a low but unknown level up to full capacity (30
gallons). I had never drained a tank and filled it from empty.
After draining the left tank, we refilled it from empty and checked my
dipstick calibration. It took only 28.5 gallons to fill the "30" gallon
tank. And my dipstick had an additional error of 1 gallon on the
generous side on top of that intrinsic 1.5 gallon error.
No significant harm to anything but the power line, a small feeder to a
single house. Deb was great, no panic, no recriminations. The whole
event spanned less than five minutes.
While maneuvering for the landing I had to make some steep turns and a
steep slip, during which her leather jacket (lying in back) slipped out
her open window. She actually was able to find it while we waited for
Chip to arrive. We call it the miracle of the jacket.
Lessons Learned
If you find yourself closely calculating your fuel range as you cross
over an available fuel supply, just land the damn thing and get more
fuel. If it's close enough to worry over, it's too close, period.
If a tank runs dry, close its valve asap.
Investing in a fuel flow meter seems ever more attractive.
I'm going to work up a set of emergency checklists. They are worth
reviewing.
--
Dan Casali
MacWizard
Box 1286 Ketchum, ID 83340
208.726.5120
[Non-text portions of this message have been removed]'
from its base in south central Idaho (Gooding) to NW Oregon. The Pacific
NW was enjoying an exceptional bit of fine weather.
We had a bit of an adventure on the way back.
The weather in western Oregon went to pot although east of the Cascade
Mts it was CAVU. On Monday, the 29th, we were delayed departing
Hillsboro, OR, (just west of Portland) until 3pm because low clouds
barred us from crossing the 1300 foot hills between the airport and the
Columbia river. We finally got out around 3 pm and slipped under the
scud over Vancouver, WA and then out the Columbia Gorge. We left with
our two 30 gallon tanks topped, and flew 3 hrs east to Joseph, OR. Six
deer were quietly grazing next to the runway as we whizzed by. They
stayed put.
There is good camping on the airstrip at Joseph and its an easy walk in
to town for great food. Good thing we were doing a bunch of walking.
The next day we left at noon for what I anticipated would be a 2 1/2 hr
flight back to Gooding. My dipsticks indicated four hrs of fuel on
board. We hit stiff winds headwinds (unusual when flying west to east)
and at 2.5 hrs were still 40 minutes to Gooding. As I overflew Mountain
Home, where I could have picked up fuel, I checked my fuel figures and
pressed on.
At three hrs the engine quit. No sweat, I think. I was expecting the
right tank to be low. I switched to the left tank and the engine surged
to life. And quit again. And surged. And quit.
I looked at Deb and told her I guess we were landing, so cinch up tight.
We were only
about 1500 ft above ground, so we didn't have a lot of time. A large
irrigated field was just behind us, rough sage and lava lands everywhere
else.
The field was an alfalfa field, and the hay had been taken in recently.
The northern half of the field was littered with hay bales and crossed
by a power transmission line. The southern half was partially being
irrigated by two parallel hand lines running east-west. I picked a path
parallel them between the sprinklers and the southern field edge. I got
off one brief mayday on 122.8.
On short final I realized there was a line of wooden utility poles
angling across my path. The choice was over or under; under seemed the
surer bet. While crossing
under the right wing struck one wire about 4 feet from the wingtip....
but the wire broke away--whew. (I later discovered the land angled down
sharply from left to right; the lowest point of the wires was not
centered between the poles. I was very lucky.)
I completed the landing and got us stopped before the end of the field.
I called Chip Gibson, my mechanic in Gooding, which was only 20 miles
away, and he came to the rescue with 10 gallons of gas. We offloaded our
gear and I flew the plane out of the field, while Deb rode to Gooding
with Chip. (Cell phones are handy; I had a chat with FSS and the FAA
while I was waiting for Chip. My mayday had been reported.)
How did I end up an hour short on gas?
I was't, actually. We found 2.5 gallons remaining in the left tank. This
was less than the 6 gallons I assumed were there, but it was enough to
get us (just) to Gooding.
I now think I understand the warning placed on my fuel valves (caution:
run on only one tank at a time) This warning was required by an
Airworthiness Directive that very tersely states:
To eliminate the possibility of engine failure due to air-lock in
the fuel system, the fuel tank selector valve should be placarded
immediately to specify that fuel be fed from only one tank at a time.
I had assumed this "air-lock" was referring to vacuum build-up in the
tank. I(and the GADO) now believe it is a quirk of the fuel system; if the
line from a tank to the carb ever runs dry the second tank will not feed
unless the first is closed off. The arrangement is gravity fed; two
lines from the tank meet at a common point (think Y) with a valve at
each tank. Without a good head of fuel, the engine just keeps sucking
air even if the valve on the tank with fuel is opened. I hadn't
immediately closed the right tank when the engine quit. I opened the
left, then got really busy.
[I got the vacuum idea from a note written in July, 1994, from C. Mack
Gavitt (the owner who financed the rebuild of N2088 in 1992-1993, to
Blake Henderson, the owner I purchased N2088 from.
"Be careful with the fuel caps. It vents thru the caps.
I'd burn one hr., Switch tanks, burn 1 hr. Repeat and then -- on
the third burn - time it until the engine burped. The theory being
that you now know how much time you have remaining. Don't use this
method. I was on short final to an Iowa corn patch when it came back to
life. Fairchild's are famous for fuel starvation problems . Check the
caps every time."
It now seems clear to me that Mack was experiencing the same type of
air-lock I encountered, a lack of flow due to insufficient head in the
tank and air flow from the empty tank.]
This explained, where did the rest of the missing fuel go? Well,I had
calibrated my dipsticks "top down"; that is, by measuring how much fuel
it took to get from a low but unknown level up to full capacity (30
gallons). I had never drained a tank and filled it from empty.
After draining the left tank, we refilled it from empty and checked my
dipstick calibration. It took only 28.5 gallons to fill the "30" gallon
tank. And my dipstick had an additional error of 1 gallon on the
generous side on top of that intrinsic 1.5 gallon error.
No significant harm to anything but the power line, a small feeder to a
single house. Deb was great, no panic, no recriminations. The whole
event spanned less than five minutes.
While maneuvering for the landing I had to make some steep turns and a
steep slip, during which her leather jacket (lying in back) slipped out
her open window. She actually was able to find it while we waited for
Chip to arrive. We call it the miracle of the jacket.
Lessons Learned
If you find yourself closely calculating your fuel range as you cross
over an available fuel supply, just land the damn thing and get more
fuel. If it's close enough to worry over, it's too close, period.
If a tank runs dry, close its valve asap.
Investing in a fuel flow meter seems ever more attractive.
I'm going to work up a set of emergency checklists. They are worth
reviewing.
--
Dan Casali
MacWizard
Box 1286 Ketchum, ID 83340
208.726.5120
[Non-text portions of this message have been removed]'