30 minute reserve

On 2005-06-14, Peter R. wrote:
Chris wrote:

If there is a head wind the difference is going be even greater.

A truly proficient pilot will plan fuel consumption based on forecasted
winds aloft for that day, any diversions needed, and then add 30
minutes (or whatever his/her personal minimums) for regulation
requirements.

And actually watch the fuel gauges. Instructors teaching that the fuel
gauges are useless (an oft-repeated canard) are teaching dangerous
rubbish. If a fuel gauge is useless it's broken and needs to be fixed.

With aircraft I regularly fly, one of the things I try to do is get a
handle on how the fuel gauges behave. I don't want to depend solely on
time for 'how much fuel do I have left' - I want the gauges to work, or
how do I tell when there's abnormal fuel consumption, or that the plane
has less than the expected fuel level? The fuel gauges should be an
important cross-check (along with knowing how much time is in the
tanks). If the fuel gauges ever show less fuel than you expect there
should be in the tank, find somewhere to land now and check it out.
Don't dismiss them.

I've already saved myself great embarrasment by having the fuel gauges
in my cross-check (I've related the story here before) - but in brief,
the gauges showed less than expected, so I landed significantly short of
my intended destination to check it out. Sure enough - the fuel gauges
were right - I had less fuel than I expected. Had I not been checking,
I'd have landed at my intended destination on fumes, probably with about
enough fuel to make a single go-around and pattern.

Now I fly across water, I'm even more paranoid about it. Most ditchings
happen because there was too much air in the fuel tanks!

--
Dylan Smith, Castletown, Isle of Man
Flying: http://www.dylansmith.net
Frontier Elite Universe: http://www.alioth.net
"Maintain thine airspeed, lest the ground come up and smite thee"

"Chris W" wrote in message
news:Uyrre.28604$rb6.27678@lakeread07...
Isn't this 30 *minute* reserve rule for day VFR flight a bit odd? Here
are 2 examples to illustrate why I say that. In a J3 Cub you are going
to go just over 35 miles in those 30 minutes. In an RV-7, you can go
100 miles with that same 30 minutes reserve. If there is a head wind
the difference is going be even greater. Both airplanes need about the
same length runway, yes I know the cub can land in less space, but both
need less than 1000 feet. Wouldn't a reserve rule that stated the
minimum distance you could fly in calm air be a better rule?


I use an hour to an hour and a half reserve as a personal minimum. Wouldn't
feel comfortable with the minimums stated in the FAR anyways...

For IFR that is what you do, you have to make it to your alternate.
However, please understand that these are minumum regulations. It is
not (and should not) be the case that if you follow every reg you will
never die. Be thankful, very thankful that the FAA allows us enough
decision making room to make our own decisions and does not regulate us
down to nothing. There are times when I've takin my plane around the
pattern to warm up the oil and not had much more than 30 minutes of
fuel, that's ok, the FAA says I can make that decision.
Don't get pulled into the "there ought to be a law" type thinking. In
reality "there ought to be a PIC" and keep the gov't at bay.

-Robert, CFI
Screw the village, it takes a parent to raise a child.

About 43 years ago I had a fuel exhaustion forced landing in an Aeronca
Sedan (15AC) on floats. It had simple plexiglas sight glass gages that
went directly into the two wing tanks - and me thinking what could be
more reliable?

What I didn't know is that it had nylon fuel cells rather than rigid
tanks. It also had leaky fuel caps and a partially plugged vent system
that allowed the fuel cell to collapse in the air. The sight glass
gages showed a comfortable half full until about 5 minutes before
complete fuel exhaustion. I landed in a swamp, drifted to shore, found
the farmer etc...... He was surprised.

In my 172M, I stick it with a Fuelhawk and never let planned landing
fuel get below 1 hour. But, I still don't really know if that hour is
really there or not except that it has never taken more than 33 (of 39
useable) gallons.

Some glider training can definitely help. You can get good at finding
updrafts so that low fuel problems need not be a concern.

Chris W wrote:
Wouldn't a reserve rule that stated the
minimum distance you could fly in calm air be a better rule?

I don't think so. You're supposed to use that 30 minutes a bit earlier in the
flight to realize that you might not make it on time and divert for fuel.

George Patterson
Why do men's hearts beat faster, knees get weak, throats become dry,
and they think irrationally when a woman wears leather clothing?
Because she smells like a new truck.

The regulation requiring this reserve on takeoff exists to make you
think about whether you actually have enough reserve fuel for your
flight. You've done this, so mission accomplished.

The rule is quite minimalist - only under the best of circumstances is
a 30 minute reserve sufficient. This is a good thing - it allows you
to go with that minimum when there is an advantage to doing so and the
circumstances allow it. It also means that the minimum isn't always
enough, maybe because you encounter unexpected headwinds or weather you
have to divert around. No big deal if airports are 5 minutes apart
where you are, but a much bigger deal if you are out over the Gulf of
Mexico. My personal minimum for overwater flights is 2 hours fuel when
I reach land, day or night, VFR or IFR. On the other hand, I consider
a reserve of 30 minutes at 45% cruise power just fine if I'm making a
day-VFR hop in good weather to an airport with multiple runways and
multiple airports within 15 minutes flying time. I'm glad the rule is
minimal enough to allow me to make my own decisions.

Air carriers have much more complex rules about fuel reserves. It's a
form of micromanagement, in a way - the rules are far more complex, far
more restrictive - and in spite of accurate fuel gauges and fuel
totalizers, lots of experience, better training, etc - airliners still
manage to run out of fuel.

Michael

Michael wrote:

I'm glad the rule is
minimal enough to allow me to make my own decisions.

Michael


A very astute and key point.

--
Saville

Replicas of 15th-19th century nautical navigational instruments:

http://home.comcast.net/~saville/backstaffhome.html

Restoration of my 82 year old Herreshoff S-Boat sailboat:

http://home.comcast.net/~saville/SBOATrestore.htm

Steambending FAQ with photos:

http://home.comcast.net/~saville/Steambend.htm

Chris W wrote:
Isn't this 30 *minute* reserve rule for day VFR flight a bit odd? Here are
2 examples to illustrate why I say that. In a J3 Cub you
are going to go just over 35 miles in those 30 minutes. In an RV-7,
you can go 100 miles with that same 30 minutes reserve. If there is
a head wind the difference is going be even greater. Both airplanes
need about the same length runway, yes I know the cub can land in
less space, but both need less than 1000 feet. Wouldn't a reserve
rule that stated the minimum distance you could fly in calm air be a
better rule?

It wouldn't be practical to require an aircraft to be able to fly a given
distance with the fuel reserve. Too many variables and they'd have to
publish distance requirements for each type aircraft. Wind, aircraft speed,
etc. A ridiculous (I know) extreme example would be to require an SR-71 to
have reserve fuel to fly a 30 minute distance at mach 3. That would be
about 900 miles.

--

Darrell R. Schmidt
B-58 Hustler History: http://members.cox.net/dschmidt1/
-

"Darrell S" wrote in message
news:07Zre.462$wV5.435@fed1read06...
It wouldn't be practical to require an aircraft to be able to fly a given
distance with the fuel reserve. Too many variables and they'd have to
publish distance requirements for each type aircraft. Wind, aircraft
speed, etc. A ridiculous (I know) extreme example would be to require an
SR-71 to have reserve fuel to fly a 30 minute distance at mach 3. That
would be about 900 miles.

I'm not sure what you're trying to say. The current regulation essentially
requires just that. It requires enough fuel to fly for 30 minutes at cruise
speed, which for any given aircraft translates into a specific calm air
distance. Each aircraft is basically given its own regulatory distance
requirement.

Under the existing regulations, the SR-71 *does* require a 900 mile fuel
reserve, if flown under Part 91 of the FARs (since it's always being
operated by the government, those rules don't actually apply...but if Part
91 was being applied, it would be applied in just the way you say is
ridiculous).

Are you trying to say that the current regulation is ridiculous? If so,
you'd appear to be in agreement with the original poster. If not, why are
you saying that the current regulation is ridiculous?

I believe that the original poster is not suggesting that each aircraft get
its own distance requirement (as is basically the case now). I believe he's
suggesting that each aircraft should share the exact same distance
requirement with every other aircraft, regardless of cruise speed.

As far as that question goes: it's my opinion that the time-based
requirement more appropriately compensates for the relevant variables. It
certainly doesn't do it perfectly, but it takes into account likely reasons
for needing the reserve, such as being off-course (thus the greater
requirement for night than for day) as well as the fact that slower aircraft
can generally use a wider range of airports, and thus won't have to fly as
great a distance to get to a suitable one.

Sure, there are clear extremes that seem to indicate some flaw in the
concept. But those are just that: extremes. The regulations couldn't
possibly address each and every situation individually and perfectly. They
simply set some guidelines -- and quite liberal in this case -- for
operation of the aircraft, and it's up to the pilot to take appropriate
steps to follow those guidelines to the letter, as well as to the spirit.

Pete