Higher performance homebuilt for a relative noob

[robertsailor1]

i wasn't suggesting that the rv had any more problems than a factory built aircraft, hence my remarks about factory built aircraft losing wings, all due to overstress as well. i am an rv fan, great aircraft but i would not pull any more g's than i would with a 172. its damn rare when an aerobatic biplane loses a wing or is overstressed but not so rare with a rv. rv's are fast and when flown by an experienced aerobatic pilot with basic gentlemen aerobatics are reasonably safe but not one i'd recommend for someone new to the game. just my opinion.

[Posthumane]

One thing I've always been curious about is how the G-rating is specified/measured/calculated on various homebuilt aircraft. In certified planes the rating is always the design load with the the ultimate load being at least 50% higher, correct? Do most homebuilt designers follow the same standards for that? I know that quality and quantity of information varies from one designer to the next, so I'll limit my question to popular lines such as the RVs.

[Colonel Sanders]

Every other RV wing failure has been root caused as gross overstress by the pilot. Hardly a problem with the aircraft

This is an extremely misleading statement. The RV is not a particularly strong or draggy aircraft, and this means that it can be extremely unforgiving of pilot error during aerobatics.

Not every RV pilot has a combat kill over Iraq, despite what they might tell you

A friend of mine, Andrew Phillips, two hangars down from me, is dead now because his RV-7A came apart in flight. He made an error - exceeded Vne - and it killed him. A very high price to pay, indeed.

I have removed the aerobatic restrictions on several RV's now - and do aerobatic instruction in them - and I cannot emphasize enough the importance of speed control, especially during a downline resulting from a botched maneuver. It is not an airplane for a beginner aerobatic pilot, but unfortunately 99% of the RV pilots are just that. A receipe for disaster.

If you fly aerobatics in an RV, keep the G and the airspeed down, and don't try any maneuver that you haven't done many times before, and might fall out of.

Heck, a friend of mine was in a gentle, high speed descent in his RV - nothing
aerobatic - and his engine oil pressure dropped (hello, Lyc 360) and his RPM
went through 4,000, trashing his engine and propeller. If you don't understand
why this happened, you're not prepared to even make a gentle descent in an
RV, let alone fly aerobatics in one.

[robertsailor1]

posthumans...yup your right all designers work to the same basic criteria. there is a difference in that factory aircraft are flown by test pilots to make damn sure that the designers were right and that includes spin testing. some of the factory aircraft did in fact show weakness that the designers didn't calculate for and the aircraft design was changed prior to production runs. The more popular homebuilts are designed by good designers and if built exactly as per plan by a good builder should give you a decent aircraft but problem is that designs are often modified by the builder and each builder becomes a test pilot but usually without the skillset. When you have a homebuilt like a pitts or an rv then there is a long track record that supports the original design. I'm old fashion when it comes to homebuilts, if its got 2 wings and was designed by a good designer (most popular aerobatic bipes all had some part of curtis pitts in them) then i'll fly them all day long. All metal aircraft by a good designer also has my vote but i'm not crazy about some of the early glass aircraft as there is really no way to inspect them.

[Strega]

Double post

[Strega]

Well, the aerobatic RV's are designed for +6,-3G. A 172 is designed for +4.4,-1.76. So I'd say they're about 50% stronger than a 172..

Careful when you make a statement such as this,,, The numbers you are referring to are limit load numbers, not design limit load numbers.

For example look at 150 and an A150,, one has a limit load of 4.4, the other, 6.0. oddly enough the empty weight of both is nearly the same. (ie no additional structure in the A150, well appreciable structure that is)

I havent done a detailed analysis of a 172 nor an RV, but I would be willing to bet the 4.4 G limit load that is published for the cessna, is more conservative to the design limit loads than the 6G is for the rv.


Mr KFC.. here is another result of loss of oil pressure in what I call a "backwards" prop, this one belonged to Kevin E

[Big Pistons Forever]

For example look at 150 and an A150,, one has a limit load of 4.4, the other, 6.0. oddly enough the empty weight of both is nearly the same. (ie no additional structure in the A150)

That is not a correct statement. The Aerobat C150 have the heavy wing struts from a C 182 and they also have heavier skins in the tail and additional doublers. The weight differential between a stock C 150 and the Aerobat is about 40 lbs.

[Strega]

Look it up in the IPC.... you will be surprised..

[robertsailor1]

The price difference back then was around 5-600 dollars which doesn't buy you too much. The quick release,extra belts and different seats to take a chute would have eaten most of that up. I do know they added some extra structure in the tail..i wasn't aware the struts were heavier.

[robertsailor1]

oh, yes i forgot the skylites

[AirFrame]

One thing I've always been curious about is how the G-rating is specified/measured/calculated on various homebuilt aircraft. In certified planes the rating is always the design load with the the ultimate load being at least 50% higher, correct? Do most homebuilt designers follow the same standards for that? I know that quality and quantity of information varies from one designer to the next, so I'll limit my question to popular lines such as the RVs.

Most amateur-built aircraft designers use the same standards that certified aircraft do... FAR Part 23. The market pretty much requires it for credibility on the part of the kit manufacturer. Unlike certified aircraft, however, there is no way to know for sure that they meet these standards. In the case of RV's, Pitts' and other well-known, many-examples-safely-flying aircraft, they have proven themselves through example if not through examination of engineering analysis. In the case of the RV's at least, wing structures have been tested to destruction at the factory, so they are very confident of their numbers. I've run rough analyses on my RV-6 and the numbers I get are certainly within the ballpark of what I would expect for a Part 23 aircraft.

Careful when you make a statement such as this,,, The numbers you are referring to are limit load numbers, not design limit load numbers. For example look at 150 and an A150,, one has a limit load of 4.4, the other, 6.0. oddly enough the empty weight of both is nearly the same. (ie no additional structure in the A150, well appreciable structure that is). I havent done a detailed analysis of a 172 nor an RV, but I would be willing to bet the 4.4 G limit load that is published for the cessna, is more conservative to the design limit loads than the 6G is for the rv.

In fact, the numbers I quoted are design limits, not ultimate limits. The easy way to remember the difference is that going beyond the Design limit is when you will bend the aircraft. Going beyond the Ultimate limits is when you will break the aircraft. The 172 can be taken to 4.4G at Utility category load limits, and live to fly another day. The RV's can be taken to 6G at their aerobatic gross, and live to fly another day.

A friend of mine ... is dead now because his RV-7A came apart in flight. He made an error - exceeded Vne - and it killed him. A very high price to pay, indeed.

I'm sorry for your loss... I followed that accident investigation closely as I own an RV and will be removing the aerobatic restriction from it this year. I even went so far as to get the "expanded report" from the TSB. It's interesting reading that contains some great lessons for homebuilders who plan to fly aerobatics.

I agree that the RV's aren't as strong as the Extra's, Edge's, Giles', etc., but (to me at least) that is clearly spelled out in their load limits. The RV is good to +6/-3, and the others are good up into the +/-10G or some ungodly high number like that (I forget the exact numbers, so don't take that as gospel... I just know that it's a lot higher than an RV on some of those aircraft).

One must always keep in mind the mission profile they expect for their aircraft... If you're looking for something to do tight, crisp airshows, an RV probably isn't what you want. If you're looking for the occasional loop, roll, etc. ("gentlemanly" aerobatics, as both Van's and CS puts it), then an RV is an excellent aircraft. Couple it with the exceptional cross-country performance and you have a truly amazing aircraft.

[Strega]

The numbers you are referring to are limit load numbers, not design limit load numbers

you didnt read what I wrote.

Just because someone says the limit load is 4.4, it might be higher...

IE the normal and utility category wrt a 172... if you are 1# overweight for the normal category, and pull 4.4G will the structure "Bend" ?

published limit loads are not necessarily design limit loads.

FYI not every airplane will shed its wings when overstressed.. for example, a mooney will loose its engine before the wing will break.

[robertsailor1]

Mooney's are a great little machine, owned 5 of them over the years. the wing spar is continous from tip to tip which when properly designed makes for a very strong wing. I wasn't aware that the engine could fall off, the way its wedged in there you would think it didn't even need engine mounts. Then along comes the rv's with fixed gear and at times fixed props and they are faster than mooney's. a few months ago i went for a ride in a pipistril virus with a 100 hp engine, damn thing stalls less than 40 knots and is about the same speed as the old mooney all the while sipping fuel. if your worried about breaking anything you pull a red handle and a balistic chute lets you down gently... things sure have changed over the last few years..night/instrument single engine doesn't have the same concerns in that little bugger.

[Beefitarian]

FYI not every airplane will shed its wings when overstressed.. for example, a mooney will loose its engine before the wing will break.

That sounds like a neat trick. I'm not doubting it but do you have any links to sources where I can read more.

[Shiny Side Up]

Apparently topics about homebuilts inevitably get into ultimate limit and aerobatic discusions. Its just one of those ways avcanada works.

viewtopic.php?f=3&t=40926&hilit=ultimate+limit

[Beefitarian]

Robert you seem to have owned or at least flown almost everything out there. What is your favorite and would you be so kind as to explicitly state why?

[robertsailor1]

Shiny side up...no kidding, reading those old posts and are you ever spot on. highly predictable i guess

[robertsailor1]

hi beef,
yup owned a few for sure but i've had a rather long hiatus so i'm not up to speed on the latest and greatest, you'll have to look for others for feedback on the new stuff. but to answer your question, planes are kinda like making love to women, none of them bad just good or better. having said that of the high performance singles i've owned..mooney, 210, bonanza, viking there was something really cool about all of them but for the shear flying experience it would be the bellanca viking, used to call it a pitts special inside a bonanza.
float planes..180 and pa-12 all moded up it was a toss up, the pa-12 with 150 hp, flaps and pa-18 tail would take off and land in a puddle. the 180 carried a better load and was much faster. i guess in the end i prefered the c-180
Fun planes, had lots of them but i had a drop dead beautiful stock stearman that to this day i wished i hadn't sold.
Bugsmashers, owned them all but the 8e luscombe was my favorite.
Least fun to fly of all the more than the 30 aircraft i've owned was the Cherokee 6..flys like a barn door.
Economical 4 place go anywhere aircraft was the piper pa-20 pacer 150 hp. outperforms most others in its class and is pretty to the eye. if i could only own one plane for the rest of my life it would be the pacer. there you go beef

[Beefitarian]

I like how you say, "I'm not up to speed on the latest and greatest, you'll have to look for others for feedback on the new stuff." Yet I know you've flown in a Pipestrel Virus. A plane I consider to be one of the up and comming "latest and greatest" but base my opinion on that from reading about them and looking at pictures online.

Thanks for the answer. Seriously, I'd trust your opinion on a new plane you flew in once over a guy that's spent all his time flying only that model. In the past I would have liked to own something exotic, perhaps in the future I can get to the point where I'm bored of the mighty Cessna singles. These days, I'd like a nice 172 or even better a 180. Due to pricing I'd be pretty happy with the easier nose dragger.

[Shiny Side Up]

These days, I'd like a nice 172

Just so happens you're in luck, Posthumane is selling his. Your kids aren't going to need a college fund Beef, so you should buy it.

In all honesty, a 172 is really all the airplane most recreational pilots really need. It can do a lot of things, if maybe not with a lot of style. These days they're also reasonably cheap, with the exception of the 2 seat bugsmashers out there, a 172 is going to be your cheapest plane to purchase and own, of the certified airplane crowd. The same could be said of the Cherokee if you prefer the wings on the bottom.

[Posthumane]

Thanks for the up-sell Shiny! Looks like you're really earning your cut of the prof- er... I mean, looks like you're providing very sound, independent advice...

The 172 is a good plane, no doubt about that, and I've considered a number of different ways to be able to keep it but reduce costs by a significant margin. A partnership is probably the best option, but I haven't had any takers on a 1/2 share that live close to me, and plane sharing between different cities several hundred kms apart is cumbersome. I do as much of the elementary maintenance as I feel comfortable, and would like to be able to do more, but I can't go back to school become an AME at the moment. Homebuilt really does look like the best alternative for me still, especially since those are the planes that really pushed me over the edge to get a license (specifically, the Zenith CH601 HDS was the plane I first fell in lust with).

[Beefitarian]

Hey, yeah. What year and model is it?

D'oh! Stupid locked registered education trust fund. I can't get that money.

[robertsailor1]

Well the only reason i got to fly the virus is that i know the local dealer and he wanted to do some aerobatics in an open cockpit biplane. i think he got the better of the deal but that little virus was quite the machine. watching the airspeed slowly build like a mooney until it was in the 140+ range was real eye opening. crazy little electric autoprop worked very well. had the big glass panel in it that verified the speeds, climb rates etc. etc. first chance for me to actualy play with one, too cool, i can see why the new bunch have trouble keeping their eyes outside. nice balance on the controls. it has spoilers that are very effective and really needed because its a cousin to a full on glider. when you think of it, its almost too good to be true...it was also slightly bigger inside than an older mooney, which doesn't take much, lol. friend sent over some pic's from the factory showing their new 4 place which will cruise along at a paltry 200+ knots, seats 4 full sized men. things are a changing.

[Beefitarian]

That sounds like the Panthera, I'm experiencing some covetious desires related to those these days. They make a hybrid which I'm sure is kind of a bad idea for maintenance costs replacing batteries and such but still facinating.

[AirFrame]

IE the normal and utility category wrt a 172... if you are 1# overweight for the normal category, and pull 4.4G will the structure "Bend" ?

According to the design of the aircraft, then yes, if you are flying a 172 at 1# over the Normal gross (or even 1# under the Normal gross, for that matter) and pull it to the Utility limit, then yes, *something* in the airplane should bend. At the very least, you should *expect* something in the aircraft to bend, if you get into that situation, and treat the plane very carefully until you can get it on the ground and inspect it.

There are probably "other" margins that companies add to satisfy their own legal departments, so I suppose it's concievable that Cessna has added an additional 20% margin or something like that to protect from ham-fisted students.