GA Aircraft & Gross Weight

[John_Cillis 2,406]

I'm still working towards my Sport Pilot license in fits 'n spurts (it's summer here and too uncomfortable to fly most weekends), and have also started to look at aircraft in this class that have come up for sale. Many don't have a gross weight that would allow two 200 lb pilots onboard with any fuel, let alone full fuel.Most responses I receive when I inquire on these ads (and I mean most) suggest that it's OK to fly over gross. My question--is it really? Wouldn't an examiner nail you on the practical if you tried to show him your stuff in an aircraft that's over gross? Not to mention that stress calculations are made with gross in mind (meaning an aircraft above gross might fail in a 2-G steep turn vs. at the G loads it's certified for)?I am curious about this. There's a lot of fine aircraft out there, but I can't imagine flying 'em over gross and not facing severe consequences if someone in the air or on the ground is hurt as a result.Any thoughts on this?Regards,John

[Tim Arnot 5]

A number of things spring to mind: What does the extra weight do to your CofG? If it moves the centre of gravity too far fore or aft, then it's a problem and will affect the controllability of the aircraft.Where are you flying from? What sort of density altitude? You mention it's uncomfortable to fly, well hot and high and heavy is not a good combination, particularly when it comes to take off.The third and maybe most serious, assuming US insurers are as keen to find a way out of paying up as ours are... any excuse will do, and you can bet they'll jump on being over MAUW as a prime excuse.Yes, all the book numbers will be for the certified MAUW

[John_Cillis 2,406]

"Where are you flying from? What sort of density altitude? You mention it's uncomfortable to fly, well hot and high and heavy is not a good combination, particularly when it comes to take off"Thanks,I believe you misunderstood the intent of my post. I am asking whether the representations and suggestions made by people selling aircraft with a low useful load to "fly over gross" are proper. My comment regarding being uncomfortable to fly is related to my ongoing SPL instruction, as I don't own any aircraft.-John

[Cessnaflyer 56]

Flying overgross will actually allow you for a slightly higher manuevering speed and turbulence penetration speed but not something I would ever want to experiment with. Unfortunately the only way for you to carry another passenger would be to go the illegal route of over gross or buy an amphib since those ones are allowed a slightly higher max gross weight under SPL regs. I find the same problems though trying to fly a F33A Bonanza with full fuel on hot days and wanting to take more then two passengers.

[lcseale53 0]

Hi John,Misrepresentations and suggestions counter to the certified design envelope of the aircraft are not proper - in my opinion anyway. However, given favorable temperature and pressure, and sufficient power, most a/c will fly above their design gross weight. From a structural perspective the math is easy. My C120 documentation, for example, states that the aircraft is designed to 150% of published max G-loadings. I'd venture to say that most of us have likely pushed (okay - exceeded) the published gross, and over a period of time you will pretty well understand the differences when on the heavy side.Interesting though, is that in many cases the airframe or engine is not the limiting factor. A friend of mine increased the published gross weight of his Glasair I 300 lbs. by simply changing the landing gear legs to a later/stronger laminate. This was a manufacturer upgrade.Another interesting comparison - My C206 has a book gross of 3600 lbs. The C182 has a gross, I believe, of 2550. The difference being 1050 lbs., and the two use virtually the same wing. The difference in allowable gross (aside from the obvious fuselage dimensional difference) is simply 300 hp vs. 230.Plenty of certified a/c have low useful loads as well. A couple of examples are the Piper Tomahawk and the 7KCAB Citabria.The Tomahawk, with full fuel (30 gals.) has a payload of about 325 lbs. The 7KCAB has a useful load just over 500 lbs. That leaves on the order of 290 lbs. in the cabin with full fuel. It's all about planning.Good luck with your training,Regards,Leon

[LAdamson 240]

In the homebuilt/experimental/kitplane market, we as the builder can set our own gross weight maximum. In the case of a Van's kitplane, where there are now 4610 known flying examples; a particular model might have a 1750 lb. gross weight recommendation from Van's Aircraft, but many builders usually go 1850 - 1900 lbs. Van's is very conservative to start with, and their planes are very tough in the design. However, Van's has used the 1750 lb. figure for their +6,-3 G calculations and CG figures. It's up to the builder to calculate differences. The FAA designated inspector might also want you to justify your gross weight, and CG figures during the inspection/signoff proceedure. You just can't go far overboard with these figures.But............in the end, almost every flying Van's RV uses a higher gross weight figure than the factory proto-types. Usually 100-200lbs.Just do a lot of web searching for real answers on the model you're interested in.L.Adamson

[Cessnaflyer 56]

You are knowledgeable about the airplanes but IIRC it is more of a limiting factor of the regs and not what the airplane is really capable of handling. Even though it could easily go over the gross doesn't mean you should continue to do that all the time. You never know when an FAA official is around the corner waiting for a ramp check. A very rare case but I know that no one would want to lose their license just to give someone the experience of flight.

[Roger Mazengarb 0]

G'day John,It is stupidity/irresponsibility in the extreme to go beyond the weight limits specified by the aircraft manufacturer/designer. These are the figures that all performance data is calculated using and final type certification is based upon.Deviate from them and you are on your own buddy! :-) and yes in it up to your neck if something goes wrong.If anyone tried selling me an aircraft saying "its OK to fly overweight if you want to carry passengers" then I wouldn't buy the aircraft off him at any price as I shudder to think what his attitude would be to costly maintenance! She'll be right mate! :-)From the tone of some other posts it's no wonder general insurance wont cover you for private flying.( and for very good reason )Some pilots seem to think that because an aircraft can physically fly overweight that it's ok to do so....What they are not telling you is that they are trading off the structural factor of safety for increased paypoad. My advice would be to look around for a different type of aircraft that has been DESIGNED AND CERTIFIED to carry the load you require.Cheers,Roger

[John_Cillis 2,406]

Thanks Roger (and to the others)Sometimes it is like pulling teeth to get an honest answer from these sellers about useful load. I am glad that I am not being a "stick in the mud" by saying no to these "too good to be true" deals. I guess my gut feeling about the Zenith and using it for Sport Pilot, or even as a stepping stone to my PPL, is a good thing. Most of them have enough useful load for two pax and full fuel. One exception (for anyone who ever considers a Zenith) are the Subaru equipped Zeniths. Many builders used the Subaru as it's cheaper than the Rotax. But it's a heavy engine--it takes an aircraft with a 540 lb useful load and soaks up 80 lbs. You wonder if these builders ever do the math before trying to save a few bucks? If you have 400 lbs of pilot and passenger and only 60 lbs left for fuel, you're not flying very safe. I think useful load is an overlooked factor when it comes to resale value of an aircraft. Regards,John

[lcseale53 0]

Umm Roger,I guess I'd like some clarification as to the comment concerning the 'other posts' and that being the reason for high insurance rates. If you are referring to the posts on this thread - please be more specific.Regards,Leon

[LAdamson 240]

> One exception (for anyone who ever>considers a Zenith) are the Subaru equipped Zeniths. Many>builders used the Subaru as it's cheaper than the Rotax. But>it's a heavy engine--it takes an aircraft with a 540 lb useful>load and soaks up 80 lbs. You wonder if these builders ever>do the math before trying to save a few bucks? If you have>400 lbs of pilot and passenger and only 60 lbs left for fuel,>you're not flying very safe. I think useful load is an>overlooked factor when it comes to resale value of an>aircraft. >John, and others.....As with Van's Aircraft, Zenith does not directly support some alternative engines, but they do list them on their website:http://www.zenithair.com/zodiac/xl/subaru.htmlVan's recommends Lycomings for their kitplanes, but another company builds a decent firewall forward kit using Subaru 4 & 6 cylinder engines. In the case of the Subaru and a Van's RV, the gross weight & weight and balance has been engineered & perfected over the years. Looking at pics from the Zenith linked web site for the "Subie", perhaps the same engineering & thought has happened there also. Gross weight is NOT written in stone, and can be changed from model to model depending on numerous factors, such as......Landing gear, aircraft structure, stall speed, rate of climb, brakes, fuel load, engine HP, etc.As I said before, I'd totally research the alternative engine websites for your particular aircraft of interest, before making any judgements. With Van's RV's, the web sites go on & on & on; and I'm sure it's the same with Zenith.L.Adamson

[lcseale53 0]

John,I'll resist the urge to dissertate, but please understand that Larry is absolutely right. Gross weight is just a vector matrix resultant, if you will - which is well defined by Larry above. Change the requirement of any one of those and you redefine the mission and suitable load...assuming structural integrity is maintained with a reasonable safety factor. Of course, in the case of a certified aircraft, you must work within the operating limitations supplied with that aircraft, which is a document, kept in the airplane, that should be committed pretty well to memory. Remember, too, that an STCd performance enhancing modification can change the operating limitations on a certified a/c. As an example, the following was noted on the Avweb site:"Power Flow Systems, manufacturer of the Power Flow Tuned Exhaust, has received FAA approval for an STC that increases the gross weight of the C172N model with the 0-320 engines. The only requirement is installing a cowl cooling lip and limiting flap travel to 30 degrees. With the additional 100 pounds, owners can plan on taking an additional 15 gallons of fuel, or an extra passenger or additional baggage."I guess the point here is that you shouldn't "throw the baby out with the bath water". Be careful assessing the merits of a particular aircraft by the misguided comments of the aircraft owner. Carefully research the aircraft and make that assessment based on the merits of the aircraft itself.Rambling done, and good job Larry,LeonOh and John, to answer your original question; part of your examination will be to calculate the weight and balance of a particular scenario on a load chart for that aircraft - so no - you do not want to authorize flight out of the loading envelope.

[Geofa 108]

My impression of the whole Sport pilot rating is that is great if you don't think you can make your medical, or if you just want to go flying by yourself in the local area, as cheaply as possible (not owning the sport plane which are more expensive "new" than a typical used single-when the used sport plane market hits perhaps this will be different).If you want to carry anything, or go anywhere, or own an aircraft as cheaply as possible, then I think the ppl is the way to go. You will spend more in the initial training costs-but you will end up with much more....You will find though that the typical 4 place single aircraft usually is a 3 person with full fuel, or a 2 place with full fuel and luggage. Still, by juggling the variables you can get much more usage and abilities imho.http://mywebpages.comcast.net/geofa/pages/rxp-pilot.jpg

[Guest tallpilot]

Hi Geof,And I'm sure you have found that the Baron "is not a 6 place airplane". :-)It's a good 2 place, lots of baggage and full fuel or 4 place, baggage and some fuel. My SUPER Viking is a good 2 place,full fuel and baggage. But 4 adults? Only if two of them are grossly under weight (90lbs) adults. So much for the manufacturer sales pitches.But even the airliners, Boeing, Douglas and Airbus can't even fly with full passenger loads that manufacturers advertise sometimes due to high temperatures/altitudes. (I Left a lot of passengers behind in Denver and Las Vegas in my day)Ed Weber a.k.a tallpilot

[Geofa 108]

Yep-part of the reason for the move to the Baron for me was the ability for 4 adults, and bags.Of course with gas prices that Viking is looking awfully good.... :-)http://mywebpages.comcast.net/geofa/pages/rxp-pilot.jpg