| by |
John Deakin |
 |
 |
 |
| About the Author ... |
|
John Deakin is a 35,000-hour pilot who worked his way up the aviation food chain
via charter, corporate, and cargo flying; spent five years in Southeast Asia
with Air America; 33 years with Japan Airlines, mostly as a 747 captain; and
now flies the Gulfstream IV for a West Coast operator.
He also flies his own
V35 Bonanza (N1BE) and is very active in the warbird and vintage aircraft
scene, flying the C-46, M-404, DC-3, F8F Bearcat, Constellation, B-29, and
others. He is also a National Designated Pilot Examiner (NDPER), able to give
type ratings and check rides on 43 different aircraft types.
|
 |
|
 |
 |
 |
|
WARNING:
The techniques and procedures described in this column can definitely be
hazardous to your health and life. I do not encourage anyone to fly at these
altitudes unless they have experience in an altitude chamber, have AT LEAST
the equipment described, and know the subject and their limitations
thoroughly.
Mountaineers call altitudes above 25,000 feet "The Death Zone,"
and they're not kidding. They are superbly conditioned athletes, very
well-acclimated to very high altitudes, often spending weeks there to get that
last little "edge" of altitude tolerance. Deaths still occur to the
best of them. Any time they do not use oxygen at those altitudes, brain cells
are dying. And yes, I've been told I've spent too much time at high altitude
without a mask!
Aside from oxygen deprivation, there is also some slight risk of
"Decompression Sickness," also known as "the bends." This
is the same problem divers face when they have been too deep, too long, or
come up too fast. A rapid climb to high altitudes may allow some of the
trapped gasses (mostly nitrogen) to expand into bubbles in the blood stream,
and those bubbles may get caught in the narrow places, especially in the
joints. This can be very painful at the least, and fatal, at worst. Those in
poor health, or the obese, are at the most risk. Pre-breathing oxygen, slow
climbs, and intermediate periods of level flight will prevent all but the very
rarest problems with DCS.
It's a hostile world, up there. I have explored it and my own limitations
slowly and cautiously over the past two years, as research for this column.
That included two flights with several people present, all on full-time
oxygen.
The Great Circle distance from Camarillo, California, to Ada, Oklahoma (ADH), is
1,107 nm. It is a fair challenge to make that distance nonstop in a Bonanza
without tip tanks, and unless there is a strong tailwind, it takes a fair
number of techniques and tricks to do it. There is also R-2501, an
"always hot" restricted area, so the 18-mile deviation north of the
direct track to bypass that adds another nautical mile to the overall flight.
Direct HEC (Hector) VOR, direct ADH was my rough plan.
I had done it easily once with my airplane (a 1982 V-35B, Serial D-10402),
when taking it to Tornado Alley Turbo for the installation of their turbo
system. As I recall, I landed with just over 10 gallons of fuel remaining.
That is my personal minimum, but only under very special conditions. To
"push it" that far, I need excellent weather at the destination, and
the final hour must be within easy gliding distance of good airports. The
logbook entry for that flight shows a flight time of 5.96 hours, and the
remarks are:
"Solo to Ada, OK for turbo. 17,500 most of the way, then 15,500'.
Lovely flight, +30 winds."
I log time from the Horizon Electronic Tach, which essentially records
engine run time, so the airborne time would have been about five minutes or so
less.
For the fun of it, I wanted to see if I could duplicate that previous
flight, this time with the turbo. Checking DUATS, my heart sank, for the winds
were not at all favorable, at any altitudes. There were either direct light
crosswinds, or very light headwinds. On another whim, I decided this would be
an excellent opportunity to try a long flight at FL290, a most unusual
altitude for a V-tail. So I punched in "direct" and took a peek.
If the DUATS computers were surprised, they didn't show it, because they
spit out the following flight plan, with RNAV waypoints off various VOR/DME
stations along the way:
Alt.: FL290
Profile: TurboBonanza
Time: Thu Aug 15 16:59 (UTC)
Routing options selected: Great circle.
Flight plan route:
PMD150018 VCV150011 HEC150018 GFS150031 EED150005 IGM150033 DRK330007
FLG150017 INW150009 ZUN330001 GUP150030 ABQ SAF180030 ACH180003
TCC180007 TXO360034 PNH180012 CDS360037 HBR360004 LAW360025 IRW180030
NOTE: fuel calculations do not include required reserves.
Flight totals: fuel: 99 gallons, time: 5:31, distance 1106.9 nm.
Average groundspeed 201 knots.
|
The weather was forecast "magnificent" (official term) all the
way, but the flight data and fuel burn were downright sickening. 99 gallons of
fuel required? My airplane only holds 82.4 gallons! Even with every ounce of
it usable (notwithstanding the lawyerese in the POH), that's a no-go. But,
wait. The parameters for that were based on flight at 210 knots TAS (true air
speed), and 15 GPH, or about 75% power lean of peak (LOP), of course. I
preloaded DUATS with those numbers right after I got the turbo, and they're
not really very close, I've just been too lazy to change them. In reality, I
commonly burn 17.4 GPH, for 85% power and 200 knots anywhere above about
12,000 feet, to 210 knots or more at 20,000 feet. I'm usually a "go
fast" kinda guy, and that power setting and speed suits my purposes, most
of the time. But it clearly wouldn't work on this flight, unless I planned to
run dry well short of ADH, and glide the rest of the way in.
What would happen if I pulled a Lindbergh, and pulled the power back? That
would reduce the fuel flow a lot (in percentage terms), while reducing the
true air speed only a little, thus increasing range. It was also apparent that
DUATS was telling me to expect about a 10-knot headwind, which pretty well
killed my chances of making the long nonstop. I thought I'd try anyway, and
just see what I could do. There are many good fuel (and food) stops along the
way, with Albuquerque an easy stop if things didn't look good. That became my
official destination, and we'd see how it went.
I've had the turbo'd Bonanza to FL240 and 250 a number of times on research
flights and a few cross-country flights, but had never gone above that, and
had no idea of what the numbers would be. WWII pilots (young and robust)
routinely operated unpressurized aircraft up to 35,000 feet for many hours at
a time, so I knew it could be done with the proper equipment and a healthy
individual. I'm very healthy, but I am 63 years old, and 40 pounds overweight,
so the usual safeguards are even more important.
In
my opinion, no one should attempt serious altitude flights without some sort
of electronic monitor that shows the percentage of saturation of oxygen in the
blood, in real time. Dr.
Brent Blue of Aeromedix first made the little Nonin "pulse
oximeter" device widely available to pilots several years ago, and in
doing so, did an enormous service to all of us. At first, the company that
invented and manufactured it Nonin (which is derived from
"non-invasive") didn't want to sell it to pilots, possibly for
fear of liability. They put up barriers by requiring a doctor's prescription.
No doctors (to my knowledge) would write the Rx, also for fear of liability.
As far as I know, Brent was the first to bypass all the fear by first becoming
a dealer, then selling the device with the prescription. Thanks Brent, we need
more people like you!
To their credit, Nonin ultimately recognized the error of their ways, and
now offers a non-prescription version of the unit (the "FlightStat")
intended specifically for pilots. The Nonin
FlightStat is a little cube a bit more than one inch on a side, that clips
onto the end of a finger. You can find an
excellent report on this little box, complete with pictures, right here on
AVweb. (For the actual manual for the unit, see http://www.mhoxygen.com/images/EDS-D1-manual.pdf)
Hospitals have been using these subminiature pulse oximeters for some time,
replacing much larger and more expensive electronics that require power from
the wall. All these magical devices work by shining a couple of beams of light
from one half of the sensor through the tissue to the other half. From the
differences in the light, the electronics determine the color of the blood,
and from that, the oxygen saturation level, displaying it digitally. It's
fairly accurate, leaving only the question of what is "normal"
saturation. Brent makes it simple. He suggests first checking for your normal
saturation at the altitudes where you live, and using 10 points below that as
a safe lower limit. I run around 97% at sea level, so about 87% is my personal
minimum. With experience, I've found this works well for me. I feel better at
the end of a long trip when I've used oxygen, and I don't think I have any
problems, at least none I admit to. When I get below 80% for very long, I can
start to notice symptoms of hypoxia and slight discomfort.
The Nonin pulse ox uses two AAA batteries, which last quite a long time,
perhaps several dozen flights, or several months. The batteries may last a bit
longer if removed between uses, if you can remember to do that. In my opinion,
the NONIN and a set of spare batteries are mandatory above 10,000 feet for any
significant length of time, for me. It is astonishingly quick to respond,
showing changes in blood saturation within a breath or two. I was amazed to
find that talking while breathing oxygen (cannula or mask) drops the blood
oxygen level very quickly! Even a couple exchanges with ATC will do this. For
some women I know
well, let's not go there.
I run a rather small 22 cu. ft. portable tank, filled from my
own two big welding oxygen tanks and the usual cannula, with the superb
little EDS 1 electronic oxygen regulator sold by Mountain
High.
This device senses the very small fluctuations of pressure in the oxygen
supply tubes from your breathing, and puffs just the right amount of oxygen
for the altitude into the cannula at the precise point when you start to
inhale. The rest of the time, no oxygen is flowing, a great savings. Mountain
High claims this will reduce the requirement for oxygen by up to 90%, and
while that may be a bit optimistic, it's really not too far off the mark, for
me. I used to make the long haul between Southern California and Seattle a
lot, and would need a fill on each end, often as much as $50 a pop. Since
airline pilots can be banned from the brotherhood for so much as actually buying
a copy of USA TODAY, my soul was in torment every time I forked over good
money, just for something to breathe. Once I began using the EDS, I routinely
used much less than ¼ of a tank for the same trip, often doing two and three
round trips before needing a fill (note this was not at FL250, but more
reasonable altitudes in the mid-teens).
[Dr. Brent Blue has taken all this a step further, and developed a device
that combines the blood oxygen sensor and something like the D-1. The blood
oxygen sensor tells the black box what the saturation level is, and the black
box automatically increases or decreases the total flow of oxygen, while still
pulsing it to occur at just the right moment. Pretty slick. I've used it, and
it works well. Last I heard, Brent is making it smaller and less expensive, so
look for it soon.]
Once the investment is made in the EDS, a "trans-filler," and a
pair of welding tanks, the use of oxygen becomes much easier and painless
(even for an airline pilot), and I normally put it on climbing through about
5,000 feet, if I'm going anywhere near 10,000 feet or above. For this long
flight at very high altitudes, I started breathing oxygen from the Aerox
mask as I taxied out.
I'm also fairly conservative about the use of cannula. Conventional wisdom
holds that they are good up to FL180, and I used them up to that (and higher)
for years - until I got the oximeter, and saw some real numbers! They just
don't do well for me at maintaining a blood oxygen level of 87% or better
above about 15,000 feet or so. I haven't seen them do very well for anyone
else, either, regardless of condition, weight, or ego. There really is a sharp
drop-off, too. Let me explain. If you check your oxygen saturation at the
elevation where you live, you'll see 95% or better. This doesn't drop
appreciably until rising above 10,000 feet, where it starts dropping very
sharply. In other words, it is not linear.
What's that? You there, in the back? What happens when you live above
10,000 feet? Go away, I'm busy, here. Move, maybe! Some people
Similarly, when I'm on oxygen (cannula) at and below about 15,000 feet or
so, the oxygen level stays up to 90% and better pretty well. But at 17,500, I
find it very difficult to keep my oxygen level above 80% with the cannula.
That's that drop-off, again.
It
is useless to kid yourself, thinking this won't happen to you. Even if you're
in very good physical condition, you MAY be even more susceptible to hypoxia
than some fat old ex-airline pilot who writes on the Internet!
During one of my research flights with Doug Ritter, I took a strong liking
to the Aerox
oxygen mask with the internal electret microphone. It fit me very well,
did better than the other masks we tested, and I found the microphone by far
the best of the bunch that we tested for
his article. (Yes, the picture there is me, at FL240, with my Aerox.)
When the test was done, I asked for a discount for the "now-used"
mask, and held onto it, mumbling something about prying it from my cold dead
hands with blue fingernails. Aerox gave me a small discount, so I was happy.
Airline pilots like discounts second only to freebies. I've used it a number
of times since, and won't go above 15,000 feet for any length of time without
it. Using it, I had been to FL240 several times, and to FL250 once without
problems, but this flight to Ada would be my first foray above that.
One
final piece of equipment that made me a lot more comfortable going so high. I
was concerned about a possible malfunction of some part of my oxygen system,
so I have a
completely independent supply that is good for long enough to set up an
emergency descent, and keep me conscious for it.
This is a green high-pressure cylinder like a large CO2 bottle, about six
inches high, with a screw-on cap and regulator valve, and a primitive rubber
mask. For storage, the cap is screwed on very lightly, barely to the point of
resistance. When needed, the cap is given a couple of quick hard turns, and
oxygen flows immediately. One hand will be required to hold this over the nose
and mouth, but I think it's an excellent backup device, and I feel a lot
better having it along.
Here's a Microsoft Excel graph of the flight, as recorded by the JPI
EDM-800 engine monitor.

Click for higher-resolution graphic
That chart looks like a chaotic mess, doesn't it? There are six hours and
ten minutes of data at six-second intervals, 3,654 data sweeps, all jammed
into one graph, and there were a LOT of changes during the flight, so it's
even more confusing than usual. For that reason, I'll break the same chart
down into six individual flight portions, and we'll see if we can sort it out
a little more clearly. My thanks to Microsoft for the magnificent Excel
program, without which we'd not have these beautiful graphs. I cuss 'em for
Windows, but a couple of their Office programs are just phenomenal.
Please take a moment to get an overall idea of what you're looking at.
(It'll help a lot if you look
at the high-resolution version.) I converted the time to elapsed time from
the JPI readout of GMT, and that is the "x axis" across the bottom.
So, the entire flight is portrayed in time from left to right, with each
individual trace rising and falling with the passing time. Only the EGT and
TIT are measured against the left side (y axis), all other parameters are
measured against the right side of the chart. The scales have been adjusted so
that everything shows on the same chart, with less interference. A couple of
the parameters have been multiplied or divided by 10, so that they will plot
on the chart with everything else. Fuel flow, for example, is in gallons per
hour, but is multiplied by 10 to make it expand, and show in a better
location. It is also shown as a heavy red line to make it stand out as one of
the most important parameters. In most cases, the absolute numbers are not as
important as the changes, relative to each other.
You may also note that MAP (Manifold Pressure) varies a lot, which is very
unusual in my airplane, because I'm always at full throttle, about 31.0 inches
MAP. In this one, I'm still at full throttle the entire time, until just a few
minutes before landing. On this special flight, I was either at such a high
altitude that the turbo couldn't maintain sea level MAP, and/or I was so
severely leaned out that there wasn't enough energy left in the exhaust stream
to drive the turbo.
This chart is expanded horizontally, and only shows the first 40 minutes of
flight:

Click for higher-resolution graphic
One of the interesting things about the recording feature of the JPI
EDM-800 is that you can't get away with anything! Everything is recorded, and
there's a reason for everything that happens. That's what makes it such a
valuable tool. Someday, we'll have airspeed, altitude and heading included in
the data stream, and it will serve as a flight recorder! It's pretty close as
is, and as we see more and more of these recording instruments in more and
more airplanes, they'll become very valuable accident investigation tools,
even if they do reduce accidents.
Note the CHT values at the start? Remember, CHT is plotted against the
right vertical axis, so all the CHTs pretty well start around 60ºF, or
ambient temperature (OAT) that day. The CHTs are slightly above that, and the
EGTs start out at about 500º to 800ºF. What's going on, here? Well, the JPI
is hooked up through the avionics bus, and doesn't start recording until I
turn the avionics master on, several seconds after the start, and the JPI
itself goes through a self-test that takes perhaps 15 seconds. So by the time
the JPI starts recording data in my airplane, the EGTs have gotten a fair head
start, and the CHTs have started a small rise, too.
The runup (marked) shows clearly, with a double fuel flow pulse,
corresponding to the two functional checks of the prop at 1700 RPM. RPM does a
double dip, and there is a corresponding rise in the MAP, although the second
pulse is not as strong, probably because I didn't wait for the RPM to drop off
as much.
Takeoff roll starts at 00:06:30, and full power is applied before 00:06:48.
18 seconds? No way, Jose! I take the power up much more quickly than that! A
quick check of the raw data for manifold pressure at that point shows, at
six-second intervals, 15.1, 19.0, 26.7, and 33.0 inches. I don't know the
delay between the actual data measurement and the data burst, but I'd guess I
started up with the power just before that 19.0 measurement was taken, and got
it to the full 33.0 inches very shortly after the 26.7 was taken, for
something just over six seconds, which is about right. "Snapshots"
at six-second intervals is the minimum interval allowed by the JPI, and while
there have been a few times I've wanted a faster sampling rate, for the most
part it's about right.
The redline MAP is 31.0 inches, so 33.0 is a bit of an overboost, but this
is common on most turbos that are controlled by using engine oil for control
of the turbo system. We've watched that on the test stand, and it's harmless.
It drives the CHT up a tiny bit faster, but by the time the airplane has
enough airspeed for cooling, the CHTs have not become critical. For those who
aren't comfortable with this momentary overboost, it's easy enough to pull the
throttle back to the redline at 31.0 inches MAP, and add it back later.
As the engine oil warms, and the MAP drops back, the fuel controller
reduces the fuel flow accordingly. The reduction to 2500 RPM (for noise) right
after gear retraction also reduces the RPM of the engine-driven fuel pump, and
this reduces the fuel flow a bit, too. These effects contribute to making this
a very easy turbo system to run, it pretty well takes care of itself.
Takeoff was on Runway 25 at Camarillo, about 10 a.m. That's obviously the
wrong direction, so I asked for an early left turn for a downwind departure.
That was approved, and I turned very early, out over the huge farmlands to get
headed in the right direction.
Since fuel burn was absolutely critical, I elected to climb lean of peak
(LOP). This is a perfectly valid technique, and will save fuel, but we do not
recommend it as a routine maneuver. With the rapidly changing altitude,
changes in speed and climb rate, ATC, and initial maneuvering, there's usually
too much going on to add to the workload. The warning system built into the
JPI makes it much better as that system will start flashing if any pilot-set
limits are exceeded.
We call that rapid transition from ROP (Rich of Peak) to LOP "The Big
Mixture Pull," or "BMP" for short. I just pulled the mixture
knob back from 31.0 GPH to 15.8 GPH over about two or three seconds. For the
next minute or two, the CHTs stayed rock solid, with the hottest at 353ºF.
After a little fiddling around, I settled on 14.2 GPH as a good setting.
Note the inversion in the OAT? 61ºF at sea level, and 92ºF at about 6,000
feet? That rise in OAT may have affected the other engine parameters a bit
more than usual, even climbing at 130 knots indicated.
At about 23 minutes, I noticed the CHTs had dropped a bit, so I increased
the fuel flow to about 15.2 GPH. The TIT and all EGTs jumped up in response,
and the CHT climbed back to about 370ºF over then next minute or two.
At about 32 minutes, note the fuel flow starts dropping off? Look at the
MAP, too. I'm guessing (based on time and about a 500 fpm climb) that this was
at about 16,000 feet, and the exhaust at this very lean mixture no longer had
the energy needed to drive the turbo fast enough to maintain sea level power.
Normally, at very rich mixtures, this turbo will hold sea level power to
20,000 feet and above, and the airplane will climb at 1,000 fpm to that
altitude. The hundreds hand on the altimeter normally runs in perfect unison
with the sweep second hand on the clock. Very nice to see a V-Tail do that!
But this was a fuel-saving flight, not a "go fast mode" flight.
At 14.2 GPH, horsepower was 212, while the normal climb would have been 300
HP. The climb rate suffers, but the airplane goes "downrange" almost
as quickly, so little time is lost.
At about 37 minutes, I ran the fuel flow back up to 15.2 GPH, which brought
the MAP back up a bit. Finally, almost 40 minutes after takeoff, I leveled out
at 17,500 feet, my initial cruise altitude. During the climb, I picked up
radar advisories from SoCal Approach, then transitioned to Los Angeles Center,
while tracking directly to Hector, using GPS.
The estimated fuel remaining at Ada, according to the JPI and GPS, was a
-9.0 (minus 9 gallons). I very nearly threw in the towel on the nonstop right
there.
This chart shows one hour and 14 minutes of flight:

Click for higher-resolution graphic
The first part of this chart reflects a bit of indecision on my part. At
this point, I knew that making the nonstop was nearly hopeless, so at one
point in cruise at 17,500 feet, I got disgusted, and just shoved the fuel flow
up to 17.0 GPH, for my usual "go fast" mode, truing out at 212 knots
TAS, and about the same ground speed. MAP was back up to 30.5", RPM 2500,
and the hottest CHT (#3) was 375ºF. I began planning lunch in ABQ, then
remembered I had a nice sandwich, a granola bar, and a couple of Diet Cokes in
the little cooler. Yum, better'n any restaurant!
But it was only just past 11:00, so I manfully resisted, and began thinking
of my intended climb to higher altitudes. At my request, ATC converted radar
advisories to IFR, and with no further ado, (eat your hearts out, East
Coasters!) cleared me direct HEC, direct "Will Rogers," with a climb
to FL230. He did specify that he wanted me OVER HEC to avoid the restricted
areas to the south, and I refrained from telling him I could skirt that area
far more accurately than he could portray it. I'd been aiming for HEC anyway,
and it only added one mile to the trip. I'd like to think that even airline
pilots see logic every once in awhile. I pitched the nose up to climb at 130
knots or so, and up we went, still LOP, of course. I made no changes to the
power setting, and expected to see CHTs rise, due to the loss of some cooling
airflow.
This is important, and it's one of the reasons we don't encourage LOP
climbs! That loss in cooling airflow can have a major effect on CHT, and very
high temperatures can result. It appears that I pulled off about 2 GPH to
allow for this (remember, when LOP, leaner is cooler).
At about that point, I got into the discussion about the restricted area
with the controller, very friendly, and also a comment or two about a Bonanza
going to 230. My response was a snappy, "You ain't seen nuthin' yet, I'll
be requesting 290, shortly!"
When I first plotted this portion in Excel, I was quite startled at the
raggedy pattern during the climb. Could I have done that bad a job? Well, in a
word, yes. But it's interesting, nonetheless.
At time 00:58:06, the oil temperature takes a sudden small jump upwards.
That is probably where I pitched up and started the climb, at the reduced
airspeed. At that same time, I pulled off 2 GPH, and got mildly distracted by
ATC, and by checking my blood oxygen.
At 01:02 or so, I realized CHTs were down, EGTs were down, fuel flow was
down to 13 GPH! This got my attention, as I thought at first I'd had a
malfunction of some kind, and it didn't make much sense. One of the things
that happens to the mental mindset after you've flown the turbonormalizer for
a time is that you're used to just setting full throttle and forgetting it,
and the MAP just sits on 31.0", essentially "forever." So I
wasn't really looking at the MAP in my scan.
I shoved the fuel flow up to over 16 GPH, to see what would happen. Sure
enough, everything headed up again, and when I finally looked at the MAP, it
was up to 29.0. I checked the throttle, still wide open, and I remember
thinking, "critical altitude," but paid no more attention. Over the
next few minutes, the same thing happened again, and again I was startled to
see EGT, CHT, MAP, and fuel flow dropping. Again, I added fuel flow, and this
time thought it through, and realized what had happened.
The next couple of spikes in the fuel flow reflect where I played around
with it for a bit, even increasing the RPM to 2662 at one point. I wanted to
see what those power settings were doing to my range, and predicted fuel
remaining. At about 01:27:00, I suddenly noticed that predicted fuel remaining
at Ada was PLUS! It was only a gallon or two, but things were improving!
Maybe, just maybe, with a little shift in the winds, and a little help, I
might get that up to my required 10 gallons, and make it after all! I also
began regretting some the of the fooling around I'd been doing, and the short
period at high-speed cruise, wondering if I'd shot myself in the fuel supply
department.
I fooled around a bit, and ended up with 11.2 GPH, 21.8" MAP (wide
open throttle), and 2173 RPM (a rough stab at 2200, I think). My indicated
speed was down to just over 115 knots, and a true airspeed of right at 170,
with a predicted fuel of 4.0 gallons in Ada. As you can see on the right end
of the chart, that gave a nice stable situation.
That also put me close enough to noontime that the rumbling in my tummy and
the tantalizing thought of that sandwich overcame me, and I decided to eat. I
don't recall trying to eat while wearing a mask before, and it's a lot more
difficult that with a cannula. A mask should be pretty secure to prevent
leaks, and mine was. I disconnected the strap that goes around the nape of my
neck, and managed to lift it just enough to sneak the end of the sandwich into
my mouth, and surveyed the world from 230 with great contentment as the first
bites hit bottom. Life is good.
At least, until I checked the oximeter, and discovered I was below 80!
Eating drops the blood oxygen level even more than talking! Steady deep
breathing in between bites brought the oxygen level back up nicely, above 90,
but it did slow down my sandwich consumption. I can also state unequivocally
that sandwich consumption reduces intelligibility on a mask mike. There must
be another corollary to Murphy's Law which states that "ATC will always
call right after you take a big bite, when wearing an oxygen mask."
"N1BE, what's the Lat/Lon for Ada, please?"
(Picture me, chomping desperately, sandwich in one hand, the other hand
holding the mask on in the absence of the strap.)
"N1BE, Albuquerque Center."
(Geez, those guys are so IMPATIENT!)
(More chomping in silence, faster.)
"N1BE, Albuquerque Center!"
"Mmmphjs, flkjelsljk!"
"1BE, say again?"
"Mmmphjs, flkjelsljk, oou erkk et!"
"N1BE, you're unreadable, can you try another radio?"
I'm not only unreadable, I'm unprintable, but we finally get it sorted out,
and I explain what had happened, much to the amusement of everyone in the
airspace. Damned smart-mouth airline pilots
Anyway, then there were comments on what type of airplane I'm flying, and
the controller remarks he's never worked a V-Tail at 230, before.
Ever the smart ass, I shot back:
"N1BE, requesting flight level 290."
There was a most satisfying silence as he thought that over.
"Uhhh, N1BE, you serious?"
"That's affirmative, requesting 290!"
He was silent again, no doubt wondering what he'd done in a previous life
to deserve a 170-knot airplane cluttering up his airspace full of 500-knot
airplanes.
"1BE, I can't do 290 right now, but you're cleared up to
270?"
"Roger, 1BE is out of 230, climbing to 270, requesting 290 if it
becomes available, and we will be a bit slow getting there."
That REALLY sparked some comments.
"You on oxygen?"
"Nah, nitrous oxide, it works better."
This chart displays only 53 minutes of the flight, edge to edge. The OAT
was at +10ºF at FL230, and dropped to -8ºF at 270, with the climb taking
only 12 minutes, an average of 333 fpm. Not too shabby!

Click for higher-resolution graphic
For the climb to 270, I first pushed the RPM up to the full 2700 (actually,
2160 to 2689, from the raw data). That large increase in engine speed caused
the fuel pump to turn faster, which ran the fuel flow up to 18.8 (the sharp
spike near the left edge of the chart). I knew that would be too high, so I
leaned it back to 16 GPH, and that worked pretty well, giving 25" MAP,
2700 RPM, and CHTs topping out at exactly 400ºF on the hottest cylinders.
Oddly enough, the #6 CHT started up with the others, but within the first
few seconds, seemed to sag behind, staying quite cold, relatively. At FL230,
the "spread" between the hottest and coolest CHTs was only about 30
degrees, but by the time I got to 270, the spread was over 50 degrees.
The scale on the chart makes this look more serious than it is, but I'm
still curious about that one. The airplane went in for annual at GAMI, and
I'll be curious to see if they saw anything that might have caused that.
At this altitude, I had the pulse oximeter on my finger full-time, and was
scanning it every few seconds. I also had the EDS-D1 in "R/M" mode
(see manual), and was watching my oxygen bottle pressure very closely. This
was NOT a time to relax, or enjoy the view, although it was spectacular. My
focus was on my oxygen level, my engine, my oxygen level, and my engine. Oh,
and my oxygen level. Comments to ATC were short and to the point, and I was
VERY aware of what I was feeling - which was quite normal, at first. To keep
the oxygen saturation up above 85%, I had to take very deep, very steady
breaths, and make a point to blow out as much as I could. At first, I was able
to hold it above 90%, but it was getting more and more difficult.
Predicted fuel remaining at Ada was up to 7 gallons, but at this point, I
was not worrying about that. In the back of my mind, I was thinking that a
long, slow descent for the final hour might put me over my required 10
gallons, but I'd worry about that later.
The good news was that the airplane was running great! 290 would have been
no problem for the airplane, and I'd bet it would go a lot higher. If I can
get the oxygen problem licked, I may someday do a column with "370"
in the title!
At about the 02:20:00 point, I experimented with various power settings, to
see if I could improve that fuel remaining, but nothing seemed to work very
well. The fuel remaining was dithering, and dropping, showing only 3 or 4
gallons remaining. Knot by knot, the effective headwind was increasing, too,
up to 18 knots, at one point. The best I could get on fuel remaining was at 10
GPH, so I left it there, still with the faint hope the winds would change, and
that a long descent would help enough.
It became more and more difficult to hold the oxygen level above 85%, and I
only rarely saw 90%. Even a quick exchange with ATC would cause it to drop
into the low 80s, and it would take a dozen breaths to get it back to 85% or
better. This was too much work! So I asked for a descent to FL250, and that
was quickly given.
This chart is only 43 minutes of the flight, so it too is expanded
horizontally. I left the fuel flow at 10 GPH, and the fuel remaining stayed
around 5 gallons.

Click for higher-resolution graphic
This is a relatively boring chart, and I haven't marked it up much. But
there is one interesting point note the fuel flow is very steady across the
chart at 10.0 GPH, which means 149 HP. But look at the CHTs? They take a
rather pronounced drop during the descent, even though the MAP rises half an
inch, and the OAT comes up, too. Then the CHTs rise again, after leveling at
250. Everything else stays pretty steady.
The answer, of course, is cooling airflow during the 2,000-foot descent
from 270 to 250, which took eight minutes. Even that small rise in airspeed
(perhaps five or ten knots) showed up on the CHT. The predicted fuel remaining
jumped up a bit, too, but I knew that was phony.
Upon arriving at 250, my oxygen saturation was back up in the low 90s, and
I figured I'd finish out the flight there if the oxygen level stayed up, and
my supply held out. It wasn't the 290 I'd hoped for, but I felt I'd gathered
some useful data.
This chart represents one hour, 50 minutes of the flight, so the data is a
bit more compact, horizontally.

Click for higher-resolution graphic
Much to my surprise, as the minutes at FL250 went by, my blood oxygen began
dropping again! What was this? Plenty left in the tank, all settings were
right, but I was, once again, hovering around 85%, and nothing I did seemed to
raise it. Once again, I made sure the little emergency system was right there,
ready for use, and reviewed what I needed to do to get on it quickly. Headset
would have to come off, mask would be ripped off without regard for the
straps, screw the bottle into the regulator hard, and put it up to my face. I
noticed that it seemed to take more effort to figure numbers out, and suddenly
when I shifted in my seat, I realized there was numbness in my left leg!
My reaction was instant. I put the gear down, and started down, HARD, at
5,000 fpm, speed increasing from 110 IAS to 155, the max gear speed, all on
the autopilot, because if I did lose it, I wanted the airplane on the
autopilot to get me down. While pushing the autopilot pitch button with one
hand, I was pushing the mike button with the other, telling ATC I had a
problem with oxygen and needed an immediate descent to 15,000 feet. Had he
come back with anything but a clearance, I would have declared the emergency,
but he sensed the (deliberate) urgency in my voice, and instantly cleared me
down. A quick glance at the oximeter showed 77%, and I started to use the
breathing pattern that had worked for me so far. It came back up slowly, and
within a minute, it was back in the 90s, long before I reached 15,000 feet.
The leg numbness went away within seconds of leaving 250, too. As best I can
tell, I lost the first 6,000 feet of altitude in one minute, 48 seconds,
without touching the engine controls.
(From the raw data, the last OAT at 0ºF was at 03:25:18, and the first
reading of an OAT of 23ºF was at 03:27:06.)
| Time |
Count |
E1 |
E2 |
E3 |
E4 |
E5 |
E6 |
C1 |
C2 |
C3 |
C4 |
C5 |
C6 |
T1 |
OIL |
DIF |
CLD |
OAT |
CDT |
IAT |
FFx10 |
RPM |
MAP |
| 03:25:18
| 2054 |
1327 |
1331 |
1341 |
1273 |
1310 |
1314 |
308 |
307 |
340 |
336 |
342 |
301 |
1376 |
171 |
68 |
0 |
0 |
146 |
56 |
99 |
223 |
200 |
| 03:25:24
| 2055 |
1321 |
1323 |
1331 |
1268 |
1302 |
1305 |
308 |
307 |
338 |
334 |
342 |
301 |
1366 |
171 |
63 |
0 |
2 |
146 |
56 |
99 |
223 |
200 |
| 03:25:30
| 2056 |
1313 |
1316 |
1324 |
1263 |
1294 |
1300 |
308 |
307 |
335 |
334 |
342 |
301 |
1361 |
171 |
61 |
0 |
2 |
149 |
56 |
99 |
223 |
206 |
| 03:25:36
| 2057 |
1307 |
1311 |
1317 |
1257 |
1286 |
1295 |
306 |
304 |
332 |
334 |
342 |
299 |
1355 |
171 |
60 |
0 |
2 |
149 |
56 |
99 |
223 |
206 |
| 03:25:42
| 2058 |
1307 |
1304 |
1310 |
1250 |
1280 |
1286 |
304 |
304 |
328 |
331 |
339 |
299 |
1347 |
169 |
60 |
-14 |
6 |
151 |
56 |
101 |
223 |
206 |
| 03:25:48
| 2059 |
1301 |
1304 |
1304 |
1250 |
1280 |
1286 |
302 |
301 |
323 |
331 |
339 |
297 |
1347 |
169 |
54 |
-18 |
6 |
151 |
56 |
101 |
223 |
212 |
| 03:25:54
| 2060 |
1294 |
1304 |
1299 |
1244 |
1269 |
1279 |
299 |
298 |
318 |
327 |
335 |
295 |
1347 |
167 |
60 |
-22 |
6 |
151 |
56 |
101 |
223 |
212 |
| 03:26:00
| 2061 |
1294 |
1296 |
1294 |
1238 |
1269 |
1273 |
296 |
295 |
314 |
325 |
332 |
295 |
1335 |
167 |
58 |
-27 |
8 |
154 |
56 |
101 |
223 |
212 |
| 03:26:06
| 2062 |
1289 |
1296 |
1294 |
1238 |
1258 |
1273 |
293 |
292 |
309 |
323 |
329 |
291 |
1335 |
167 |
58 |
-31 |
10 |
154 |
56 |
101 |
223 |
217 |
| 03:26:12
| 2063 |
1289 |
1289 |
1289 |
1232 |
1258 |
1268 |
289 |
289 |
303 |
320 |
325 |
289 |
1330 |
167 |
57 |
-35 |
10 |
154 |
58 |
101 |
223 |
217 |
| 03:26:18
| 2064 |
1289 |
1289 |
1283 |
1232 |
1252 |
1268 |
285 |
285 |
298 |
316 |
321 |
286 |
1330 |
164 |
57 |
-37 |
14 |
156 |
58 |
103 |
223 |
217 |
| 03:26:24
| 2065 |
1289 |
1289 |
1283 |
1232 |
1252 |
1268 |
281 |
281 |
293 |
313 |
318 |
284 |
1330 |
164 |
57 |
-40 |
14 |
156 |
58 |
103 |
223 |
222 |
| 03:26:30
| 2066 |
1289 |
1289 |
1283 |
1232 |
1245 |
1268 |
277 |
278 |
288 |
310 |
313 |
281 |
1330 |
166 |
57 |
-40 |
16 |
158 |
60 |
103 |
221.8 |
222 |
| 03:26:36
| 2067 |
1280 |
1289 |
1283 |
1232 |
1245 |
1263 |
273 |
274 |
283 |
306 |
309 |
278 |
1325 |
166 |
57 |
-42 |
16 |
156 |
60 |
100 |
217 |
222 |
| 03:26:42
| 2068 |
1275 |
1279 |
1278 |
1232 |
1245 |
1263 |
269 |
270 |
279 |
303 |
305 |
275 |
1325 |
166 |
47 |
-42 |
19 |
154 |
60 |
100 |
217 |
216 |
| 03:26:48
| 2069 |
1275 |
1279 |
1278 |
1232 |
1245 |
1263 |
265 |
267 |
276 |
299 |
302 |
273 |
1325 |
176 |
47 |
-42 |
21 |
152 |
60 |
97 |
215.5 |
216 |
| 03:26:54
| 2070 |
1270 |
1279 |
1278 |
1227 |
1245 |
1263 |
261 |
264 |
273 |
296 |
298 |
270 |
1319 |
176 |
52 |
-40 |
21 |
150 |
60 |
99 |
215.5 |
216 |
| 03:27:00
| 2071 |
1270 |
1279 |
1278 |
1227 |
1245 |
1263 |
258 |
260 |
270 |
293 |
294 |
268 |
1319 |
171 |
52 |
-37 |
21 |
150 |
60 |
99 |
216.1 |
216 |
| 03:27:06
| 2072 |
1270 |
1279 |
1273 |
1227 |
1245 |
1256 |
254 |
257 |
267 |
289 |
291 |
265 |
1319 |
175 |
52 |
-39 |
23 |
148 |
60 |
95 |
214.5 |
216 |
When things go bad at those altitudes, they go bad very quickly!
I was prepared to cut the power for the descent, but once I saw how fast I
was able to come down with the gear down and resulting slow rise in the speed,
I thought I'd just leave things alone. As I recall, I broke the descent at
about 180, pulled the gear up, and made the rest of the descent a bit more
sedately. This shows up in the much more gradual slope of the OAT rising to
35ºF at 15,000 feet.
Look at the rest of the traces on the chart. Note how precipitously the
CHTs drop with the huge increase in airspeed, and no change in power. Even the
EGTs dropped a bit, which surprised me.
During the final stage of the descent, the MAP rose enough to drive the
fuel flow back up a little, from 10 GPH to 12.6 GPH. Remember, at no time
during this flight did I ever touch the throttle, it was wide open the entire
time. Any change in the MAP is due to other factors, mostly those driving the
turbo.
It took me about five minutes to catch on to the increased fuel flow and
remember I'd had 10 GPH set, so I pulled the mixture back to 10.0 GPH. I was
surprised to see the predicted fuel remaining had risen to 8 gallons! The wind
had changed enough during the descent to nearly "create" enough fuel
to make the long nonstop! If only I hadn't wasted some fuel, early on!
The fleeting thought "Maybe landing with 8 is okay?" I swatted
that thought like the bug it was.
Alas, it was not to be, as the wind steadily began shifting around to my
nose again, and I began the search for a good fuel stop. Hobart (Oklahoma) looked
good, and the JPI/GPS told me I'd have about 13 gallons left if I landed
there. It was the only one around with "Fuel, 24 hours," so I
figured it was a good bet.
Alert readers may spot the little downward spike in most of the parameters
just after time 04:57:06. What was that? Here's the raw data for it:
| Time
| Count |
E1 |
E2 |
E3 |
E4 |
E5 |
E6 |
C1 |
C2 |
C3 |
C4 |
C5 |
C6 |
T1 |
OIL |
DIF |
CLD |
OAT |
CDT |
IAT |
FFx10 |
RPM |
MAP |
| 04:56:48
| 2969 |
1311 |
1314 |
1328 |
1290 |
1297 |
1299 |
283 |
282 |
319 |
307 |
316 |
291 |
1353 |
173 |
38 |
0 |
33 |
123 |
66 |
91 |
207.4 |
211 |
| 04:56:54
| 2970 |
1311 |
1314 |
1328 |
1290 |
1297 |
1299 |
283 |
282 |
319 |
307 |
316 |
291 |
1353 |
173 |
38 |
0 |
33 |
123 |
66 |
91 |
207.4 |
211 |
| 04:57:00
| 2971 |
1311 |
1314 |
1328 |
1290 |
1297 |
1299 |
283 |
282 |
319 |
307 |
316 |
291 |
1353 |
173 |
38 |
0 |
33 |
123 |
66 |
91 |
207.4 |
211 |
| 04:57:06
| 2972 |
1311 |
1314 |
1328 |
1290 |
1297 |
1292 |
283 |
282 |
319 |
307 |
316 |
291 |
1353 |
178 |
38 |
0 |
33 |
123 |
66 |
86 |
205.4 |
211 |
| 04:57:12
| 2973 |
1303 |
1308 |
1316 |
1283 |
1282 |
1292 |
283 |
282 |
319 |
307 |
316 |
291 |
1345 |
183 |
34 |
0 |
33 |
123 |
66 |
84 |
205.4 |
211 |
| 04:57:18
| 2974 |
1269 |
1264 |
1280 |
1261 |
1265 |
1260 |
283 |
282 |
319 |
307 |
316 |
291 |
1320 |
187 |
20 |
0 |
33 |
119 |
64 |
79 |
210.1 |
198 |
| 04:57:24
| 2975 |
1302 |
1307 |
1310 |
1272 |
1271 |
1286 |
281 |
280 |
316 |
307 |
316 |
291 |
1345 |
178 |
39 |
-13 |
33 |
121 |
64 |
90 |
205.9 |
214 |
Note the first 18 seconds (three time snapshots) are normal, but on the
fourth row, the fuel drops from 9.1 to 8.6, to 8.4 six seconds later, and to
7.9, before turning right around and going back to 9.0.
That's where my right tank ran dry, of course.
I had flown the first hour (exactly) on the left tank, then used the right
tank for 3:57, for an average burn of 10.43 GPH, which seemed about right.
Knowing I'd climbed that first 40 minutes or so at 17 GPH (LOP), I now knew I
had to have about 24 gallons remaining, and the JPI confirmed that. Finally,
the left fuel gauge showed just over ½, another confirmation, as I know from
experience my gauges are exactly correct.
With all this, I had ample evidence that I truly did have 24 gallons
remaining, and this satisfied one of my requirements for pushing range to land
with only 10 gallons remaining. At this power setting, it was about an hour's
fuel, which even satisfies the FAA rules!
So there I was, fat, dumb, and happy, at 15,000 feet, resolved to land at
Hobart, burning 10 GPH, and poking along at about 170 knots TAS.

Click for higher-resolution graphic
Knowing I now had nothing to lose, I thought I'd see how much leaner I
could go. I leaned, and leaned, and leaned, and finally found just a trace of
roughness at 6.5 GPH, or so, or 97 HP. I enriched just a hair, and the engine
was baby-bottom smooth at 6.9 GPH, or 103 HP! This wasn't even enough power to
stay in the air, I had to begin a gentle descent to stay above 110 IAS! This
is just about 250º F lean of peak EGT. Yes, the engine WAS running, but just
barely.
It bears repeating, this is still at full throttle! This demonstrates the
extreme power control from mixture alone.
6.9 GPH didn't even give enough power to make the airport, so I had to boot
it up to about 12 GPH, and finished with a fairly normal 45 minutes on the end
of the flight.
The long slow descent was uneventful, except the headwinds continued
building, and I ended up landing at Hobart with just 11 gallons remaining.
Yes, I did reduce throttle to land! I did have one scare, as I turned short,
very high final, I realized there was NOTHING at this airport! No airplanes,
no cars, no sign of human habitation or activity, just 30 knots of blowing
dust! The one redeeming feature of this desolate airport was a gleaming new
24-hour gas pump, self-service. What a relief!
As I taxied up, I wondered, "Will my credit card work?" When it
did, and I heard the machinery come to life, I wondered, "Is there enough
gas?"
There was, and I finished up with the 20-minute flight to Ada. Sorry, no
data for that leg.
Be careful up there!