172 Weight and Balance

[5X8B]

Hello.. Don't want to open a big can of worms, but I have a question on Wb.

I know you really can't fit 4... say 200 pounders in a 172 without being over weight.

Say you have 3 200 pounders in the plane with full fuel and oil, it puts you over weight by 20 or 30 #'s.

Question is; Could you still fly 20 to 30 pounds over weight for a bit until you burn some fuel off without being unsafe? If so, what will the airplane feel like?

Of course I'm using numbers on the high end...

[Jeppesen]

Depends how you define "safe". Will it fly? Yes...but it won't climb very well. The plane will feel very "heavy" and underpowered.

[yakdriver]

Will it fly and handle ok? Depends on the day. If you have cool temps and low density altitude. Here is another scenario for you. You are loaded 100lbs under gross but it is 95 degrees and the airport is 3000' long at 6500' MSL. Do you think your going to get off and climb out? Don't be stupid this early in your flying carrier, look at your load and performance charts and add a fudge factor on the safe side not the other side. Will you get away with an overgross airplane, sometimes but not every time. Don

[UHBlackhawk]

You can probably get away with it. The problem comes if something goes wrong. All your performance numbers will be off and you may well also be out of CG.
Also be aware that when NASA did some spin testing on GA airplanes they found some to be very unpredictable (read unrecoverable), when above gross weight.

[hm]

Little planes are routinely flown hundreds of pounds overweight, loaded down with auxiliary fuel tanks, in order to take them over large stretches of water. A 172 in Europe got there on its own power. This is done, legally, with an FAA waiver.

What you're proposing is illegal. It is done all the time, though. The guy ferrying the plane to Europe is presumed to know what he's doing, and to have ensured a proper CG, and that the plane meets the necessary climb and runway performance for the fields he's using. He's presumed to understand the impact this has on maneuvering speed.

The average pilot who does this is pretty much just rolling the dice based on the fact that he's only a "little bit over", and pretending that he's really at MGW. Yes, this works, in a "close enough" sense. But, again, it is illegal, and it's easy to let success with 30 lbs over lead to a try with 60 lbs over, and for that success to inspire trying 90 lbs over... Eventually, you have the plane loaded up with lardos and full fuel on a hot day, and you end up in the trees.

Or, maybe more likely, one day you end up with some kind of unrelated mishap, a botched landing, and the NTSB and the insurance company start doing some math...
-harry

[jerryp]

When one of my students asks me this (it's usually a surprise when I have them do a W&B in a 152 with my fat fanny and full fuel), I always tell them to think about what other pilots will think when they read the NTSB report should something go wrong.

I got lazy recently with a new student and his older Cherokee 140. Before we started lessons, I did a full set of stalls, a power off landing and steep turns to make sure there were no bad habits. I did not do a W&B before flying, instead taking his numbers home and plugging them into my spreadsheet.

Turns out with him, me and full fuel we were under gross but outside the CG envelope forward. We now fly with <30 gallons of fuel.

[AceAirspeed]

Question is; Could you still fly 20 to 30 pounds over weight for a bit until you burn some fuel off without being unsafe? If so, what will the airplane feel like?

The answer is an emphatic NO! Just because it will fly, does not mean it is safe. The decision itself to do this is unsafe regardless of the chance of success. What mission is so important that you want to exceed the published capability of the plane? And if you decide to do this, make sure you tell your passengers, "Hey guys, the manufacturer says I shouldn't do this, but I know better."

[Gimble]

Could you still fly 20 to 30 pounds over weight for a bit until you burn some fuel off without being unsafe? If so, what will the airplane feel like?

Issues, as listed above, are center of gravity, performance, and legal ramifications. I don't think I can add much to what was said above.

However, consider this: as airplanes age and go through various changes, they tend to gain weight. It's not uncommon that when an airplane is finally re-weighed (e.g. after a paint job) that it suddenly has another 0-100 lbs. empty weight.

Now, in your scenario: if the plane has another 60 lbs. of empty weight that isn't currently reported (and thus you do not know about), do you really want to fill it to gross + 30 lbs or so? What's that going to do to your performance numbers?

[HIGHwing]

However, consider this: as airplanes age and go through various changes, they tend to gain weight. It's not uncommon that when an airplane is finally re-weighed (e.g. after a paint job) that it suddenly has another 0-100 lbs. empty weight.

Another point on how that rule of thumb it typically applied. Usually it's stated that as a model ages, or matures it gains weight, i.e. the Cessna 1XX will have a lesser basic empty weight as an "A" model as opposed to a "S" model.

The reason this happens is obvious, we like more stuff, manufacturer adds "stuff". Interestingly there is a certain point at which this breaks the other way. Take any airplane with an original King Stack in it. Those radios require a module to do every little thing, most people would be shocked to see all the crap that goes into making a King 170B have Glideslope, etc. Anyway, the point is that you can remove a large King Radio, Glideslope Receiver, DME, ADF, indicators, power converters, and more just by swapping in a GNS-430 which is lightweight itself and uses about 30 pounds less wiring. Swapping my King Stack for a Garmin stack (which has a ton more capability) netted over 64 more usable pounds than when it left the factory, and my airplane has been repainted.

All this is to say, I agree, it's somewhat pointless to use book numbers when the real numbers are readily available with the airplanes documentation.

[5X8B]

Thanks all for the response. Just to let everyone know that I would NOT do this. I was just more curious than anything. But it does mean I should get back to the gym to shed some extra pounds.

Thanks again!

[EppyGA]

Thanks all for the response. Just to let everyone know that I would NOT do this. I was just more curious than anything. But it does mean I should get back to the gym to shed some extra pounds.

Thanks again!

And when you climb on the scale you'll think in terms of half gallons and gallons instead of pounds.

[angryweb]

Thanks all for the response. Just to let everyone know that I would NOT do this. I was just more curious than anything. But it does mean I should get back to the gym to shed some extra pounds.

Thanks again!

That's funny. I started going to the gym again in order to both lose weight for flying and make sure I never have an issue with my medical. Oddly enough, flying has made me live a healthier life in all aspects.

[Warever]

Or, maybe more likely, one day you end up with some kind of unrelated mishap, a botched landing, and the NTSB and the insurance company start doing some math...

Yes, but how are they going to know how much fuel was on board when the whole thing is a smoldering mess? (and all the fuel burned in the post-crash fire)

(dark humor there...)

[jerryp]

Another point on how that rule of thumb it typically applied. Usually it's stated that as a model ages, or matures it gains weight, i.e. the Cessna 1XX will have a lesser basic empty weight as an "A" model as opposed to a "S" model.

Age is a double-whammy. The older the plane, the less likely your are to actually get the performance numbers in the book, which were developed by a test pilot with a new airframe and engine.

[Benchracer52]

And when you climb on the scale you'll think in terms of half gallons and gallons instead of pounds.

lol - thats great - I am good for 2 extra gallons fuel in the plane since Christmas