I can't say how common partial fuel loading in order to increase pax load is nowadays in the industry, but it is a great way to set up a fuel starvation event.

If I were being pushed to do partial fuel loads to add a couple more pax, I would give the DZ two options, neither of which they are going to like-

1. Provide a calibrated fuel hock (dipper) certified in writing by a mechanic with gallon increments. You may be able to buy one already made somewhere. The mechanic will obviously charge to make one, because he will have to drain out all the fuel and refuel the airplane to calibrate the stick, which is a big chore.

2. De-fuel as necessary pound for pound in order to accommodate each added passenger over a normal pax load starting with a topped off fuel load. This is a bigger pain than getting a calibrated dipper made. No DZ in their right mind will go for it, but you should offer this option to show them you are serious about not having a fuel starvation event on your watch.

Using the fuel gauges or any other method is a gamble against the luck of the pilot. I discourage any new DZ pilot to gamble with the fuel load using home made dippers, fuel gauges, and guesswork. You'll really regret it if you have a fuel starvation event. It will haunt you for life as a pilot.

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On the steep spiral question, you absolutely can unport the fuel taps doing steep spirals on the descent. You need to keep the fuel loads balanced left to right by alternating direction of turn on the hops. Do not get past your allowable load/ hop count, and I discourage playing with the fuel selector to balance tanks because you will forget to select it to "both" sooner or later. The gauges are not trustworthy on old 182s either, so do not use that to do it.

Unfortunately we usually have a classic time-building situation; "if you won't do this, sonny, there are ten others waiting in line behind you".

It was a common practice when I was diver-driving. We only filled up one side of the ole 182 about half way and left the other side dry. I never noticed any serious performance issues but you damn sure had to keep track of your fuel burn. Usually re-fill after about 3 loads.

How is this happening if flight is coordinated?

I've flown me lots of C182, and something I've noticed is that certain older ones are notorious for not burning out of tanks equally during all flight maneuvers and especially S&L when on "both", even leading to fuel starvation issues as at least one was not taking fuel out of one side reliably, even when selected, but other than that, how would a steep spiral cause one side to be uncovered, unless you are yawing the whole way in a slip?, which wouldn't be the best way to drop altitude as far as stresses on the aircraft in any case.

Who said it is coordinated. I used to do a "knife edge" slip all the way down, purposefully uncoordinated. Let me see if I can find the pictures of that. See my post no. 4 on the thread below for an explanation of the knife edge steep spiral. If done correctly it is the fastest way down and was/is used for decades by various drop zones. Structural issues arise when pilot technique is shoddy, and I would not recommend doing this maneuver without a g meter even with a decent pilot. You want to push 3 g's and no more, but poor pilot technique can lead to over g'ing the airplane.

Knife edge thread

I'd trust it as long as it was homemade by me :D

Well, you can do a steep spiral and come down very fast without being uncoordinated at 60 degrees of bank, not to mention that I think most people assume coordinated flight unless specified otherwise. The FAA recently put out some stuff on using more than one control surface to input full deflections and Va, although I'd assume this is done slow enough where it's no problem. It's more than just pilot technique, it's knowledge and sometimes misunderstandings as to what the aircraft was really rated/intended for. I just don't see any major reason to do this uncoordinated. I've done plenty of high bank angle "knife edge" slips, but if I was taking people up flight after flight, I'd think equal fuel is a more important consideration.

While this knife edge steep spiral is very hard on a 182 if not done correctly, many limit of the performance envelope maneuvers are done for many reasons in training and operations, and it is not a valid argument in itself that simply because it is risky we do not do it. Where the advantages outweigh the disadvantages, like in student training, air shows, and in skydiving ops we do high risk maneuvers. And do them carefully. Like any high risk action, we manage the risk carefully to reduce it and control it.

Knife edge steep spiral is only done in smooth air. You need to knock it off and quickly slow to Va if not, and in this case you would never speed past Va if you knew there was rough air around. We are talking about a drop zone where you fly the same profile 20-30 times a day. You know what the winds are.

However, the fastest way down in this airplane is this maneuver, which explains why it is used. If you do not believe me then call some drop zone who use it and ask why. They do not do other types of rapid descents because they simply take longer and time is money. It's a question of rate of wasted of potential energy in physical terms. The uncoordinated steep turn wastes a large amount of energy height.

Like said, I have done thousands of turns of this maneuver, never a single fuel issue. This is due to my careful risk management- I carry enough fuel not to unport anything.

I actually agree with this statement. Drop zones will not allow their pilots to do serious steep turns or other edge of flight envelope tasks if they cannot train them well enough to do it safely. If there is a high pilot turnover and/or poor pilot training they will stick to easier maneuvers. That's why we see the other kinds of descents being used.

I know technically its rated for it but 3 g descents all day every day would sure be rough on the air frame after a while wouldn't it? In most cases these 182's and other piston airplanes at most drop zones are half a century old. I'd say it's more cost effective in the long run to save the frame, gyros etc. and come down nice and easy. I'm getting 2000-25000 ft per minute descent with a wings level nose down attitude.

A correctly done steep spiral knife edge maneuver in a 182 can push 5,000 fpm in the descent. Maybe that sheds some light on why it is so useful. I have obtained that descent rate many times, two minutes from door shut to touchdown. Like I said several times it takes some skill, and it is not something you want newbies doing. On the other hand, you get so much practice at a busy drop zone there is no reason anyone cannot work it up over a period of days or weeks which is what I did.

As for loading the wings to 3 g's, it works fine all day every day. In material science there is something called the elastic limit of a material, which is the stress limit where complete recovery of the strength of the material occurs without permanent damage. Drop zone experience has it that 182s can go to the mid +3g range for decades without exceeding this limit. Above that to the certified limit of +3.58 works fine too, but you have no margin for error going that high in normal operations. Beyond that up to about 4.5 you will not fold a wing right away, but you will start popping rivets on top of the wing. If you do that enough times you will pop a lot of rivets, and beyond that you may fold a wing. Go right to 5+ and you may fold a wing without warning. There is a company that has tested 182 wings to this level (and was not Cessna). I'll see if I can dig up that reference.

Another relevant question is, what is the life cycle load limit- it does decrease with time, but it is such a high number that no drop zone with any vintage 182 has ever found any change (reduction in limit) as far as I know. And I have asked if there are any. of the data I have examined, there is no evidence that load limits have come down within 50 years of normal operations over which data was collected.