Gross Weight

"Michael" wrote in message
oups.com...
I know that when I was receiving training, my instructor
once had me bring 2 male adults with me to a lesson.

He then had you project performance and handling characteristics by
extrapolating from the POH and maybe other sources. In flight, he
discussed these issues with you so you would know how to handle the
situation in the future, pointing out quirks of the operation. No? He
just told you to get in and go?

I wish that were the exception, but it's the rule. He was teaching you
how to fly overgross, and he was doing about the worst possible job of
it. Yeah - you did it in that particular instance. You learned a
little - mainly, you learned that operating outside the published
envelope has consequences, and a bit about what they can be. But
without an underlying framework for understanding, all you learned is
what happens in that one specific case. Since that specific case is
unlikely to be repeated exactly, you haven't really learned anything
very useful.

So the answer to your question of how much is too much? When the
safety margin associated with the limiting factor in play under the
circumstances becomes uncomfortably slim, that's too much.

Michael


Very nice post, and I enjoyed reading it. I especially like your view on
what my instructor did, and you make a very good point. I have admitted to
myself, that he did some things in my training that, although we got away
with, were wrong, and I remember those each time I fly. You make a very
good point with regard to teaching without the proper framework. I will
also remember that. Thank you for you comments.

Fred

Excellent post!

I have two comments...

If you fly overgross, you're breaking the rules. Where
will the rulebreaking stop? The answer is really nowhere.

I agree. But as you pointed out earlier, keeping within max gross won't
keep you safe, either. In other words, every flight includes making
decisions about performance that are arbitary, or more precisely, that
are based on experience. If experience didn't matter, why would we keep
log books? If the rules were enough, why would we need anything else?

You can study the design, and the available
modifications and authorizations, to determine
if it is performance, rather than structural integrity
of some component, that limits gross weight.

If it is structural issues -- which I would suggest it very rarely is
-- you'll still have a huge safety margin when 5% or 10% over-weight.
You are not going to be getting that close to the 'g' envelope, and
your landings are hopefully not going to be hard enough to be given 10%
of collapsing the gear!

Further, if you look at accident reports where over-weight operation
was a factor, I doubt you'll find many where structural issues came
into play. In fact, I can't recall reading a single one, and like most
pilots, I eat 'em up to try and learn from others' mistakes. As I said,
the failure mode that matters most is failing to fly, or failing to get
out of ground effect.

If it is structural issues -- which I would suggest it very rarely is
-- you'll still have a huge safety margin when 5% or 10% over-weight.
You are not going to be getting that close to the 'g' envelope, and
your landings are hopefully not going to be hard enough to be given 10%
of collapsing the gear!

The answer to this is - it depends. I agree - the average flight does
not take you anywhere near the limits of the g-envelope. However,
momentary loads of 3 gees or more are not unheard of when flying in
moderate turbulence. So for a VFR flight under a stratus overcast,
sure, I wouldn't worry. For an IFR flight in cumuliform cloud, with
scattered embedded T-storms, I would reconsider. Note that while the
ultimate design load is 150% of the rated load, there is no requirement
for the structure to withstand the ultimate design load without damage.
Deformation is permissible. Repeated deformation due to excess loads
may be a problem. This all assumes the key structural components were
correctly manufactured in the first place, and have not deteriorated.
With an aging fleet, that may not be all that valid. However, I will
grant you that for a utility category aircraft, this is not an issue
worth considering.

The same issue comes up with regard to landings. Long smooth runway in
daylight and light winds, in a plane I've flown before many times? No
problem. Unfamiliar airplane and short strip with gusty crosswinds? I
think I want all the protection I can have. How tough is the gear,
anyway? When effectively the same gear is being used on an airplane
with a significantly higher gross weight, that tells you something (the
gear has plenty of margin). When you have a max landing weight lower
than the max takeoff weight, that tells you something too (the gear has
no margin - it is maxed out). Just something to think about.

Further, if you look at accident reports where over-weight operation
was a factor, I doubt you'll find many where structural issues came
into play. In fact, I can't recall reading a single one,

See the NTSB references in my reply to cwk.

Michael

The same issue comes up with regard to landings. Long
smooth runway in daylight and light winds, in a plane I've
flown before many times? No problem. Unfamiliar airplane
and short strip with gusty crosswinds? I think I want all
the protection I can have.

Agreed 100%. As I said before, it's about JUDGEMENT.

See the NTSB references in my reply to cwk.

I looked at these, both of which were for Cessna 402Cs, which I think
immediately says something about whether we're dealing with a general
or model-specific issue. The first, for N819BW, happened when the spar
broke where it had been subject to mechanical damage AND deep machining
marks. Hardly sounds like being over-weight was the cause here. The
second, N405MN, can't really be put down to anything, since very little
of the airplane was recovered. Again, hardly a clear case of
over-weight operation causing structural failure.

"Mike Granby" wrote

Further, if you look at accident reports where over-weight operation
was a factor, I doubt you'll find many where structural issues came
into play.

Right. I seem to remember that maneuvering speed (the max speed for not
over stressing the airframe in turbulence, or hard maneuvers) is higher, for
a more heavily loaded aircraft.
--
Jim in NC

Fred Choate wrote:
How much is too much over gross weight?

I will not fly 1 pound over gross, I will not delibrately break an FAR, I
will always do a thorough pre-flight on the aircraft, I will only cancel IFR
once I'm more than 500' below or 1000' above the clouds, etc. As a CFI, I
have canceled lessons because the compass card was missing or not legible -
perhaps the cancelation proves to be a better lesson for the student in the
long run than the instructional flight. Either way, I'm not prepared to be
tempted by the slippery slope.

NAFI Code Of Ethics: http://www.nafinet.org/who/code.html

Hilton

Hilton

Have you ever drained 5 gallons of fuel out of an airplane to get it
under the maximum gross weight?

Have you ever cancelled the Lesson due to the missing compass
correction card while instructing/flying was your only source of income
and you haven't flown (or been paid) for 3 weeks due to bad weather?

What do you do on your Dual Cross countries when any of the following
occur 100 miles from your home airport and 30 miles from the nearest
Mechanic? And you have 3 more students waiting for you when you get
back since they haven't been able to fly for past 3 weeks due to bad
weather.

1. The Starter Fails
2. The Alternator Fails
3. The Trim Tab Indicator Breaks off
4. The Flap Position indicator Fails
5. The Compass Correction Card Blows out the Window.
6,. You discover the Fluid has all drained out of the Compass
7. Screw falls out of the Cowling
8. Transponder Fails
9. Brake Fails
10. Vacuum Pump fails
11. Stall Warning become inoperative
12, Flap motor Fails


True flying with some of these failures is not even illegal. on the the
other hand I have almost all of them occur to me at some time or
another if not mulitple times.

The Vacuum pump failed about 1 hour into my 1st solo Cross country. Not
a big deal.

Anyway the point is I doubt the statement "I will not delibrately break
an FAR" would hold up many in these situations. Perhaps I am wrong in
your case if so I suspect you are in a unique situation and more power
to you.

Also remember that many aircraft are crashed or damages without ever
breaking a FAR.

Brian

Brian wrote:
Have you ever drained 5 gallons of fuel out of an airplane to get it
under the maximum gross weight?


Good God... no. Nor will I. I'd never be welcome there again.


Have you ever cancelled the Lesson due to the missing compass
correction card while instructing/flying was your only source of income
and you haven't flown (or been paid) for 3 weeks due to bad weather?


I can tell you at least have operated with the constraints placed on someone who
flies for a living. These simplistic rules of thumb I've been reading from the
self righteous here are making me want to spew. Simple rules are for simple
people.


What do you do on your Dual Cross countries when any of the following
occur 100 miles from your home airport and 30 miles from the nearest
Mechanic? And you have 3 more students waiting for you when you get
back since they haven't been able to fly for past 3 weeks due to bad
weather.


You tie down the airplane, set the brake, set the throttle (gently) and hand
prop it. Then you fly it home IFR (I follow roads). I've had most of that crap
happen to me one time or another too. My last 135 cargo company expected us to
continue to the destination on one engine if the other failed; they didn't get
paid otherwise. That's the reality of flying for pay. You don't get the
privileges of flying for fun.



--
Mortimer Schnerd, RN

VE

As a CFI, I have canceled lessons because the
compass card was missing or not legible - perhaps
the cancelation proves to be a better lesson for the
student in the long run than the instructional flight.

Yeah, right. And I'm sure the guy who took time off work, drove to the
airport, and then had you cancel on him 'cos the bloody compass card
was ilegible was really pleased with the lesson you taught him. It's up
to you how you teach, but I'm glad my CFI had a more realistic
attitude.........

Mike wrote:

As a CFI, I have canceled lessons because the
compass card was missing or not legible - perhaps
the cancelation proves to be a better lesson for the
student in the long run than the instructional flight.

Yeah, right. And I'm sure the guy who took time off work, drove to the
airport, and then had you cancel on him 'cos the bloody compass card
was ilegible was really pleased with the lesson you taught him. It's up
to you how you teach, but I'm glad my CFI had a more realistic
attitude.........

For the record, "the guy" finished his Private with me, wants to do
recurrent training with me, wants to get checked out in other aircraft
models with me, and if/when he does his IR, he said it'll be with me.

Not all the lessons to be taught during training are in the air.

Hilton