How do you determine what a "safe" overweight condition is?

In Alaska you can fly over gross.

Section 91.323 does not allow flying over gross. That section appears to only provide for what is essentially a re-certification at a higher maximum weight in limited circumstances. And it is not an automatic re-certification.
 
So let's say you're going to take off from a 5000 foot runway in a 172 that is 200 lbs over gross. It's early morning and nice and cool. No clouds in the sky, no bumpy air. No obstacles when you take off. You're going to land right at gross once you've burned off your fuel... Illegal yes but safe to fly?
 
So let's say you're going to take off from a 5000 foot runway in a 172 that is 200 lbs over gross. It's early morning and nice and cool. No clouds in the sky, no bumpy air. No obstacles when you take off. You're going to land right at gross once you've burned off your fuel... Illegal yes but safe to fly?

Maybe safe (maybe), but still stupid.
Every time you overstress the airframe you risk weakening something.
You just don't give up, do you?
 
If you like being a test pilot.
 
Maybe safe (maybe), but still stupid.
Every time you overstress the airframe you risk weakening something.
You just don't give up, do you?

Why overstress the airframe? I did say no bumps. Surely the only result is an increased Vr and a reduced rate of climb but otherwise no real additional forces?

I'm just trying to understand. I guess I don't just accept something "because somebody says so". I need to know why.
 
Two hunters got a pilot to fly them into the Alaskan wilderness, where they managed to bag two big Bull Moose. As they were loading the plane to return, the pilot said the plane could take only the hunters, their gear and one moose. The hunters objected strongly saying, "Last year we shot two, and the pilot let us
take them both and he had exactly the same airplane as yours."

Reluctantly the pilot, not wanting to be outdone by another bush pilot, gave in and everything was loaded.
However, even under full power, the little plane couldn't handle the load and went down, crashing in the wooded wilderness. Somehow, surrounded by the moose, clothing and sleeping bags, Stosh and Stan
survived the crash.

After climbing out of the wreckage, Stosh asked Stan, "Any idea where we are?"

Stan replied, "I think we're pretty close to where we crashed last year."
 
I did say no bumps.

I've had huge "bumps" come out of nowhere and with no warning.

Would you "probably" be safe 200 lbs over? Probably.

But it's a numbers game.

99% safe means once every hundred times it won't be.

99.9% safe means once every thousand times.

Fly enough, and the improbable can start to become a near certainty.

And it only takes once.

But different pilots have different risk tolerance - and that risk tolerance is often on display in accident reports.
 
Section 91.323 does not allow flying over gross. That section appears to only provide for what is essentially a re-certification at a higher maximum weight in limited circumstances. And it is not an automatic re-certification.

I'm not trying to argue semantics, there is a blanket gross weight increase for certain operations with NO basis of engineering. Two identical aircraft one flown in the lower 48 and the other operated by the department of the interior in Alaska doesn't have anything to do with physics, airframe stress, longevity, turbulence, etc. it is simply a license for "certain people" to speed. I doubt those operating under this provision consider themselves test pilots.
 
So let's say you're going to take off from a 5000 foot runway in a 172 that is 200 lbs over gross. It's early morning and nice and cool. No clouds in the sky, no bumpy air. No obstacles when you take off. You're going to land right at gross once you've burned off your fuel... Illegal yes but safe to fly?
If someone here says yes, are you going to do it?
 
In Viet Nam, 1968.......we'd fly our Huey (UH-1H) from Camp Eagle down to Danang for a load of beer. If we could pick the load up to a hover just above sea level down at Marble Mountain Airfield we figured we could haul it over the Hai Van Pass :D
 
In Viet Nam, 1968.......we'd fly our Huey (UH-1H) from Camp Eagle down to Danang for a load of beer. If we could pick the load up to a hover just above sea level down at Marble Mountain Airfield we figured we could haul it over the Hai Van Pass :D

That was with someone elses' aircraft. And I suppose the risk of flying overweight was minimal when compared to other risks you took.
By the way, I'd like to send you a virtual salute!
 
You have safe and then you have legal.

Legal is the engineers [and lawyers] best guess at safe if inside the loading envelope.

Safe is where you have enough CG and engine power to safely climb away from the runway and maneuver normally. . . . that number differs with loading and runway length and hp.
 
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Good place to mention that performance is only one criteria for determining max gross weight.

Many planes are limited by structural limitations (or chute capability) rather than HP.
 
If someone here says yes, are you going to do it?

No.

But if someone says yes and has a convincing argument why based on facts not opinions then....maybe ;)
 
That's great man!



Just a small detail I would prefer not to actually "share" a drink if that is okay with you. You have your drink and I have mine and maybe the bottles touch but no more than that.



See you there.


We are soooooooo going to steal a drink of your beer now, knowing that you'll just hand it over willingly. Man, I need to go re-do my OSH beer budget now. ;)
 
In Viet Nam, 1968.......we'd fly our Huey (UH-1H) from Camp Eagle down to Danang for a load of beer. If we could pick the load up to a hover just above sea level down at Marble Mountain Airfield we figured we could haul it over the Hai Van Pass :D


Ha. I like it.

Welcome Home.
 
No.

But if someone says yes and has a convincing argument why based on facts not opinions then....maybe ;)

Assume you one day weigh all the facts and decide 200 lbs over is safe.

And, on takeoff, a tire blows or a brake locks, causing a swerve into runway signage. Totally unrelated to the overweight condition, let's say.

If the NTSB shows up with scales, how much "weight" do you think the FAA will give to your assertions of safety based on information gathered on the internet?

It's your license, but any time you fly over gross by even 1 lb, your license could be at risk.

A small risk, maybe. It's your license so it's your choice.

BTW, I lost a rental plane and two lives were lost when a renter chose to fly my Citabria over gross. Other factors were definitely in play, but "links in a chain" and all that.

http://www.ntsb.gov/aviationquery/brief.aspx?ev_id=20001208X07205
 
Why overstress the airframe? I did say no bumps. Surely the only result is an increased Vr and a reduced rate of climb but otherwise no real additional forces?

I'm just trying to understand. I guess I don't just accept something "because somebody says so". I need to know why.
Well for starters the landing gear is designed for a specific maximum load.
And do you understand the concept of lift? The wings are designed to provide sufficient lift to offset the drag (weight). Push either one of them past their limits too much or too often and metal failures can occur. I like my wings to stay attached.

But more importantly than that, Pilots are proud of themselves as a group. When a pilot does a dumb thing that causes a crash it makes us all look bad. Not only that, but when crashes hit the news it makes flying look dangerous and scares the bejesus out of our families and friends, and it puts up more roadblocks to other people that are thinking about getting into flying. The more pilots there are the better it is for all of us. Part of the reason aircraft parts and supplies cost so much is that the market is limited and profits have to be made from a dwindling customer base.

But mostly, pilots are proud and smart. Other pilots doing dumb things is embarrassing.

edit to add: I'm not saying that asking questions is a dumb thing. But indicating that you may do things after more experienced people give you reasons not to can be. And whether something is dumb or not, if it is illegal, then doing it IS dumb.
 
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And whats up with this doublespeak:
"NTSB investigators either traveled in support of this investigation or conducted a significant amount of investigative work without any travel".
:dunno:
Perhaps there were multiple investigators; some of them traveled and some didnt'.
 
I did know the fellow, but just as a student/renter. He was a very experienced pilot.

I did allow aerobatics in the plane, but only after checking out the pilot in particular maneuvers. He was not checked out, and did not ask for parachutes that day. Most of my renters just liked flying the plane and the tailwheel aspect and solo aerobatics was pretty rare.

Off topic, but we never figured out the missing wing attach hardware issue. There was no reason it should have been removed for any reason. I was in the gym business, and just watched "Pain and Gain", which was based on a real gym (Sun Gym) who was a local competitor. The case was turned over to Broward Homicide, but I think they had nothing to go on to indicated foul play.

Still makes me wonder if I may have been a target. Don't think I'll ever know for sure.

In better times, at Hollywood Aviation at N. Perry:

10467045524_dfd0b9f9e2.jpg
 
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No.

But if someone says yes and has a convincing argument why based on facts not opinions then....maybe ;)

Just do it. Load it up with as much as you desire and give it a shot. When you bore a hole in the ground you will be held liable for damages to the aircraft, even if dead (estate), as insurance will walk away.
But please, don't take our word for it, go out and do it.
 
And whats up with this doublespeak:
"NTSB investigators either traveled in support of this investigation or conducted a significant amount of investigative work without any travel"
Not directed towards you, just happened to notice it.

Boilerplate language to distinguish 'desk investigations' based on FAA fieldwork from accidents that had an ntsb investigator from the start. There is a way you can tell from the accident number.
 
Well for starters the landing gear is designed for a specific maximum load.
And do you understand the concept of lift? The wings are designed to provide sufficient lift to offset the drag (weight). Push either one of them past their limits too much or too often and metal failures can occur. I like my wings to stay attached.


Yes wings remaining attached would be nice!

So if I'm 200 lbs over max in a 172, that is about 10% over the limit. Aren't the structural elements all designed for loads that are 50% over the anticipated maximum? So being 10% still gives me some margin does it not?
 
Yes wings remaining attached would be nice!

So if I'm 200 lbs over max in a 172, that is about 10% over the limit. Aren't the structural elements all designed for loads that are 50% over the anticipated maximum? So being 10% still gives me some margin does it not?
Do you realize that you are talking about your life and the life of those on the grounds under you? I'll accept a 10% risk if we are talking about petty stuff. Is that how you rank your life, your passenger's lives and the poor schmuck that is in bed sleeping when you bore a hole in his roof?
 
Do you realize that you are talking about your life and the life of those on the grounds under you? I'll accept a 10% risk if we are talking about petty stuff. Is that how you rank your life, your passenger's lives and the poor schmuck that is in bed sleeping when you bore a hole in his roof?

All he will be talking about is how he got some uptight sticklers on some aviation board all riled up over nothing.

172s get ferried 20% over gross with big bladder tanks in the back. But hat is done by experienced ferry pilots off long runways. No, the wings dont fall off, but you wont be able to go around with flaps which creates the mtow limitation in the 172.
 
Why do we always get into all this "Boogey Man" talk when discussing weights?

Let's think about this. Linked is an example STC (there are many) that raises the gross of an A36 to 4,000lbs. with the addition of tip tanks. That is over a 10% increase. There are NO modifications to the engine, gear, wing, brakes, prop, or anything else that matters. I guess if I have that piece of paper I am safe to fly in any and all conditions that I used to do at 3600. Further if I leave the tips empty, then I am WAAAY safer than I was before I added the weight of the tips, right? If someone could just add enough things to an airframe they would never have a problem with weight again:)

http://www.jlosborne.com/Site/images/Press Release Letter.pdf
 
Why overstress the airframe? I did say no bumps. Surely the only result is an increased Vr and a reduced rate of climb but otherwise no real additional forces?

I'm just trying to understand. I guess I don't just accept something "because somebody says so". I need to know why.

"Why" questions are best answered by a four year degree in the field you are inquiring about. Then you can wax eloquently on the subject until your listeners ears bleed. Having said that, here's a very, very brief primer.

There are two ratios that are very important in plane physics. The first is wing loading. If you take the area of the wing, and divide the max gross weight of the plane, you get the wing loading. Like this:

2200Lbs/150SqFt = 14.666666... *I don't know the actual wing area of a 172, so bite me

Now, if we start adding weight, without adding wing area we get into the point where the increased angle of attack will be too high in drag for the plane to fly or climb:

2600/150 = 17.333333333... *the wing did not 'grow' any

As the wing loading number increases, the angle of attack of the wing to produce added lift makes the plane hard to handle, and at some point, the wing will need to be going so fast at take off that it will have no reserve lift for climbing out of ground effect. This is notwithstanding the engine power which we'll get to next.

All airplanes, and all wing shapes are not created equal. The 1960 Piper Pace has a rather short, fat wing which is suitable for a range of speeds between about 55-145MPH. No matter how much engine you hang on the 1960 Pacer, at some point, that big fat wing will no long push through the air with any amount of weight and that is the limit of that. The Piper Aerostar has a thin wing more suitable to high speeds, and the takeoff speed is concomitantly higher as well as the wing loading.

Next we cover power loading. Like wing loading, we take the weight of the aircraft and divide it by the HP:

2200Lbs/145HP = 15.17

As with wing loading there are limits involved. To have greater climb, and go a tad faster Cessna has upped the HP of the 172 over the years, and improved the speed a bit, as well as upped the weight as well. Numbers for a 172Q:

2550Lbs/180HP = 14.1666...

Suppose we used the higher weight of the later year, with the lower HP of the early year:

2550Lbs/145HP = 17.59

As with wing loading, power loading has limits. It works together with wing loading to maintain a safe margin of HP to weight so the plane has sufficient reserves to climb. Some planes have higher limits, or one might say lower margins. This is not to say that a plane with 2550Lbs and a 145HP and 150SqFt of wing area, won't work, But the design margins have been compromised, and the operation in all situations would be less than the designer intended. You are - in effect a test pilot because you are operating outside the boundaries of the design parameters.
 
Why do we always get into all this "Boogey Man" talk when discussing weights?

Let's think about this. Linked is an example STC (there are many) that raises the gross of an A36 to 4,000lbs. with the addition of tip tanks. That is over a 10% increase. There are NO modifications to the engine, gear, wing, brakes, prop, or anything else that matters. I guess if I have that piece of paper I am safe to fly in any and all conditions that I used to do at 3600. Further if I leave the tips empty, then I am WAAAY safer than I was before I added the weight of the tips, right? If someone could just add enough things to an airframe they would never have a problem with weight again:)

http://www.jlosborne.com/Site/images/Press Release Letter.pdf

This isn't entirely true. There is a modification to the wing. There was a Naval engineer who did a series of tests on the Bonanza back in the day, and was quite well versed in aero-engineering. He was able to show with some pretty convincing cacls aided by some very well instrumented flight tests that the tip tank produces a better span-wise efficiency of the wing much like a blended winglet would. It's not exactly the same, but the effect of the big bullet out there keeps the air flow from rolling off the end of the wing, and makes the tip area more effective at producing lift.

I'm pretty sure that his calcs along with some serious testing by JLO are the basis behind the increased MGTOW due to the better wing efficiency provided exclusively by the installation of the tip tank. I think the C-310 is also aided by the same design feature, but I know nothing about the 310, so that's just a guess.
 
This isn't entirely true. There is a modification to the wing. There was a Naval engineer who did a series of tests on the Bonanza back in the day, and was quite well versed in aero-engineering. He was able to show with some pretty convincing cacls aided by some very well instrumented flight tests that the tip tank produces a better span-wise efficiency of the wing much like a blended winglet would. It's not exactly the same, but the effect of the big bullet out there keeps the air flow from rolling off the end of the wing, and makes the tip area more effective at producing lift.

I'm pretty sure that his calcs along with some serious testing by JLO are the basis behind the increased MGTOW due to the better wing efficiency provided exclusively by the installation of the tip tank. I think the C-310 is also aided by the same design feature, but I know nothing about the 310, so that's just a guess.

I heard that argument, I'm not qualified to rebuff, so OK. My personal experience doesn't agree, but I digress. I would suggest that anyone who wants to test whether or not tip tanks increase performance over 10% come up to the mountains in summer in a NA A36 and take-off at 4,000 and see how it goes.

More to the point, here are a couple of pure paperwork gross STC's.

http://flighttraining.ventura.aero/gross-weight-stc/

http://ercoupe.info/uploads/Main/grossweightSTC.pdf

etc.

My point is simply that there are many STC's for many types that require no serious modifications.
 
I heard that argument, I'm not qualified to rebuff, so OK. My personal experience doesn't agree, but I digress. I would suggest that anyone who wants to test whether or not tip tanks increase performance over 10% come up to the mountains in summer in a NA A36 and take-off at 4,000 and see how it goes.

More to the point, here are a couple of pure paperwork gross STC's.

http://flighttraining.ventura.aero/gross-weight-stc/

http://ercoupe.info/uploads/Main/grossweightSTC.pdf

etc.

My point is simply that there are many STC's for many types that require no serious modifications.

When you capitalize 'NO modifications to the ...., wing,' that would be wrong. That's what I'm trying to point out.

I've flown early Bo's(not A36) with and without tip tanks. They handle different, and they climb different. If the FAA says it's ok, and the pre-takeoff DA calcs say it ok, then it must be -- ok, right? :D Given your mtn situation a tip-tanked A36, flying within the DA parameters is no longer a test pilot. However, if the weight is 4001Lbs, then he/she is a test pilot. But under that magical limit, modified by the tip tank install and the STC, it is no longer test pilot zone.

Sorry you don't like the argument, I didn't do the calcs, and the link is no longer valid or I would provide it for you.
 
Thanks docmirror, very interesting!
 
When you capitalize 'NO modifications to the ...., wing,' that would be wrong. That's what I'm trying to point out.

I've flown early Bo's(not A36) with and without tip tanks. They handle different, and they climb different. If the FAA says it's ok, and the pre-takeoff DA calcs say it ok, then it must be -- ok, right? :D Given your mtn situation a tip-tanked A36, flying within the DA parameters is no longer a test pilot. However, if the weight is 4001Lbs, then he/she is a test pilot. But under that magical limit, modified by the tip tank install and the STC, it is no longer test pilot zone.

Sorry you don't like the argument, I didn't do the calcs, and the link is no longer valid or I would provide it for you.

I stand corrected.
 
This discussion brings a story to mind. When I was going through my flight training in a Cessna 172SP, one day I asked my instructor if I could bring my 13 year-old daughter along as a back seat passenger. He said, yeah, no problem, so long as weight and balance are fine. I said she weighs about 105 pounds, and he said "should be no problem". But we didn't actually do the math until a week after the flight when we were were going through some ground training on weight and balance calculations. I'm a pretty big guy and so was my instructor, and it turns out that between the two of us, my daughter (who it turns out weighed closer to 120) and full tanks we were about 40 lbs over weight at take-off. :(

But the plane handled just fine. My instructor seemed a little embarrassed but was willing to shrug it off as a testament to the built-in margin for safety on the published limits. Thank you Cessna for that!
 
I wouldn't be surprised if a great many flights are above gross "accidentally".

A lot of people lie about their weight or quote their weight naked even though they presumably plan to fly clothed :rolleyes:. So you take three passengers each underweighing themselves by 10-15 lbs then bringing a bag which is really 45 lbs and not "about 30 lbs" as they told you. I know this from experience being a passenger on other flights. Add that all up and the pilot flying might think he is only at gross but could easily be 50-60 lbs over.
 
This discussion brings a story to mind. When I was going through my flight training in a Cessna 172SP, one day I asked my instructor if I could bring my 13 year-old daughter along as a back seat passenger. He said, yeah, no problem, so long as weight and balance are fine. I said she weighs about 105 pounds, and he said "should be no problem". But we didn't actually do the math until a week after the flight when we were were going through some ground training on weight and balance calculations. I'm a pretty big guy and so was my instructor, and it turns out that between the two of us, my daughter (who it turns out weighed closer to 120) and full tanks we were about 40 lbs over weight at take-off. :(

But the plane handled just fine. My instructor seemed a little embarrassed but was willing to shrug it off as a testament to the built-in margin for safety on the published limits. Thank you Cessna for that!

For my PP check ride years ago the DPE invited my CFI to come along. This was in a 180 hp C-172N. I had run W&B on my spreadsheet for that condition just for chuckles and grins, but it was great to hand the printout to the DPE when she suggested it and say, "We're legal".
 
I heard that argument, I'm not qualified to rebuff, so OK. My personal experience doesn't agree, but I digress. I would suggest that anyone who wants to test whether or not tip tanks increase performance over 10% come up to the mountains in summer in a NA A36 and take-off at 4,000 and see how it goes.

They dont improve performance. They move the plane from utility to normal category and the plane benefits from some shuffling of the paperwork.

Many owners of A36s that have gained MTOW based on turbonormalizing or tip-tanks forget to read the POH supplement that comes with the modification. Some of them indicate a 30% increased take-off distance for flight at weights above the originally certified MTOW.
 
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