And What's Next?
By ANN Correspondent Kevin O'Brien
A teardown Sunday morning revealed
why Bruce Bohannon fell short of his planned US absolute piston
altitude record -- and the entire, disappointed crew breathed a
sigh of relief. It was a broken, formed bracket, that prevented the
wastegate from closing fully and the engine from developing full
power in the rarefied air near Bohannon's 50,000 foot
objective.
How come? Well, if an airplane might be broken, it makes sense
to ask a mechanic you catch working on it.
"There's a bracket for the wastegate," Ernie Butcher explained.
(Unlike most modern turbos, whose designers to reduce pilot
workload and maximize efficiency with an automatic wastegate, the
Flyin' Tiger's Mattituck MTX-555 engine has a manual wastegate, to
give its pilot, Bohannon, maximum control). "And of coures, at
about 40,000 is the time where it starts getting almost
closed."
"And at 45, he really makes sure it is closed. [But] that
bracket is fractured, so it didn't get quite closed, so he didn't
get full power."
So that's all it was, a wastegate bracket? A little metal
bracket?
"Well, that was certainly a significant part. He can go higher.
He's BEEN higher."
That would be 47,067 feet, Bohannon's current FAI Absolute
Altitude Record in Class C-1B, set at Flyin' Tiger Field in Texas
in November, which earned Bohannon his third straight Louis Bleriot
medal from the FAI (an accomplishment unprecedented in FAI's long
history).
Another factor? High ambient
temperatures at altitude. While the FAI corrects alitude and other
records for standard atmospheric conditions, the thin, hot air had
a dual effect, aerodynamically on the Flyin' Tiger's airframe, and
on the Flyin' Tiger's engine. Between the wastegate's inability to
fully close, and the extra degrees, the usually robust-and-a-half
MTX-555 was wheezing -- at least by MTX-555 standards.
"We thought that there was no reason for this. And everything
was perfect when he went up! I mean, we looked at it, we went over
it, we took it apart, we inspected it. But -- you know."
Yeah.
"When you're out there on the edge sometimes...."
Well, could it have been damage that had been somehow missed?
With that thorough inspection cycle, and the quality of the Exxon
Flyin' Tiger maintenance crew, it seems unlikely. Still, the day
before the flight, we were surprised to note that the engine had
been removed. As it happened, a foreign object had FODded the
turbo, and it had in turn made a mess of the exhaust; the turbo and
some of the exhaust parts had to be R&R'd in very short time
before the record flight. Still, we saw some of this work going on,
and like everything the team does, (at least in sight of the press
and public!), it took place with consummate professionalism and no
drama at all. So COULD the wastegate bracket been damaged in the
turbo failure, and somehow missed until the record flight, despite
the inspections?
"It could have been a fracture that we didn't see." So it was
possible that it was damaged in this way. It could have been that
the initial failure was a tiny crack that was too small for human
eyes to detect, also. The bracket failing on the record flight,
though, seems more probable than a preexisting failure.
"And of course, it gets quite a bit
of tension on it, when he closes the wastegate."
To lose a record because of a small alloy bracket. That's
disappointing.
"To say the least."
What about the absolute world record of over 56,000 feet?
Bohannon will be unlikely to attempt that in the Flyin' Tiger. The
limiting factor is high-altitude physiology. While a positive
pressure O2 system can sustain life to FL 500, beyond that point
the pressure is so low that the nitrogen in human blood boils; you
need a pressure suit or pressure cabin, which add weight and
complexity.
"This plane wasn't built for that. It was an afterthought [to
pursue altitude records.] He just seemed to do wo well flying
it..."
It must be unbelievably cold in this thing, at forty-something
thousand feet.
"I wouldn't get in it, anyway."
So, anyway, that was why the long tradition of Bruce Bohannon
and te Exxon Flyin' Tiger record-breaking at airshows was
interrupted this summer.
"We just found this this morning," Butcher said, looking back to
his work under the control panel of the Flyin' Tiger, and no doubt
wishing the reporter would shove off and let him do it. "I'm glad
we found something legitimate. None of it made sense. It was SO
perfect going up."
And he had done it before.
"Oh yeah. He is more motivated now than ever." Most likely, the
team will tackle the record where they set the last one -- Flyin'
Tiger Field, deep in the heart of Texas.
A lot depends on other things -- like sponsors. But here, the
team members have no worries. The sponsors great and small have
been outstanding.
"Well, Exxon -- and Mattituck --
I've been around this [business] for a long time and I've never
seen two sponsors with more support. The folks that did the turbo,
we sent it back in -- Kelly Aerospace -- it's just unbelievable.
They're all --" and he gestured at the array of sponsor decals
festooning the side of the record-shattering Flyin' Tiger, sweeping
all the smaller sponsors into the circle of excellence with Exxon,
Mattituck, and Kelly. "He's just got the cream of the crop here --
but then, he's a cream of the crop kind of person."