What would you build? 9A or 7a?

Hi Everyone,

Although I recently started to take flying lessons, I am sure I will eventually build my own airplane and since I don't like working with composites (I use to own a sailboat...) I will build an RV. I am inclined to go the quickbuild route.

Since overall building costs seem similar, what would you build? An Rv9A or Rv7A?

I don't whant to start building a 9A and by the time I am finished (with more flying experience) regret not having built a 7A.

A this particular moment the primary use for the plane would be cross country flying.

More experienced advice would be greatly appreciated...

Fred Minlos
Ontario, Canada

I had to make the same decision and didn't know which one I'd rather have.

I don't care about stalling a little faster so I didn't see the 9 with any advantage over a 7. The 9 can take engines smaller than the 7, which I like, but it then get too slow (for me wants, it's still plenty fast).
A 7 can do accro, but I'm not planning on it. The 7 has a higher gross (I doubt for everyday operation it will ever be a factor for me).

I'm working on a 7.

I had the same question a few months ago. If you do a search, you can find lots of prior discussion about this. Since you are new, I'd recommend that you get a ride with an aerobatic pilot so you can see if this appeals to you. The short answer is that the 9(a) was designed for efficient cross country travel and the 7(a) was designed for fun (noncompetition) aerobatics, but is quite capable of cross country trips as well. Also, if you can, get a ride in both to see what you think.

I'm working on a 9a.

Biggest difference is aerobatics. I've been flying my -6 for over 13 1/2 years and love it. I like turning it upside down occassionally. I fly out of a 1500' strip in Texas and it's not a problem. Having said that, if I built another RV it would be a -9. I like the low speed characteristics and as I get older, the acro gets less and less. Not that much difference in cruise speeds. You won't go wrong with either (unless you like acro). But as said before, there are lots of examples out there. Get a ride in both before deciding.

Why I chose 7A QB

1. Shorter wings - easier to hangar or share hangar
2. Shorter HS - easier to hangar or share hangar
3. Cheap to use 180 hp FP, get all the climb of 160 hp CS with simplicity
4. 100 NM greater range with IFR reserves for comparable speeds per Van's own numbers and my calculations (assumed 20kt HW, etc.)
5. Stall speed slow enough (50-55 kts IAS without fairings just tested) to compete with my C-150 but able to handle XW takeoffs and landings better than the -9A because of shorter wings and slightly higher touch-down speed
6. Stronger, thus greater margin for turbulence.

There are some good reasons to choose the -9A. These are just the ones that helped me choose as I did. I am non-aerobatic, 800 hours in 29 years, mostly in C-150's and C-172's. Flying my -7A is very easy and the landings are better than in my 150, probably because of ground effect. I love it. You cannot go wrong with either one IMHO.

building a 7a

but now after flying for a while i believe a 9 would better suit my desires. have no intention of doing acro. thought i did. but i doubt it. maybe a roll or two. already had an 0320. but since i went fp prop i like the 180 on the front ..both are great planes. fit your profile. just cause i have an acro capable craft doesnt mean i have to. but the other way around i dont have a choice. so i guess the seven is better fro me.. a nine isnt a trainer.its a stable platform. notice the desire for autopilots on the 6,7,8s. they can be a hand full esp IFR.
that doesnt concern me though cause im a master pilot just kidding i have zero intention of flying IFR...will have the auto pilot later.

cytoxin said:

a nine isnt a trainer.its a stable platform. notice the desire for autopilots on the 6,7,8s. they can be a hand full esp IFR.
that doesnt concern me though cause im a master pilot just kidding i have zero intention of flying IFR...will have the auto pilot later.

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A 9(a) with a two axis A/P and constant speed prop will make a great flying airplane. Wouldn't want one without them! It was a 9a that finally spoiled me with it's auto-pilot system, after a series of long cross-country's.

And the C/S does wonders for getting it down quickly, when desired, not to mention a whole lot better for high altitude airports.

L.Adamson

Focus on your flying lessons

dvc4you said:

Although I recently started to take flying lessons...

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Learning to fly and building an airplane are mutually exclusive activities -- each alone will consume all of your available free time. It's fun to dream about planes you might someday own, but not nearly as much fun as simply learning to fly.

Focus on your lessons. Or better yet, postpone the lessons until you find a good, mid-time, re-sellable trainer to buy (like a Cessna 150 or Piper Cherokee 140). Once you outgrow the trainer, the question of which airplane to step up to will probably answer itself. Right now you don't know what kind of flying you like, so how could you possibly make the right choice about which RV to build?

If you're careful about the trainer you buy, you can easily save the cost airplane rentals while you're training -- probably more than $5K. You might even make a little on it when you sell. Certified airplanes (and RV's) are like houses. They tend to appreciate if you buy right. By the way, you can probably find a good trainer for a quarter of what you will spend building an RV!

Researching, buying, and owning an airplane is a hoot all by itself. Hang out at the airport and join your local EAA chapter. You'll have no trouble finding guys who will fall all over themselves to help with your search. You can't throw a rock at an EAA meeting without hitting an A&P.

It's all about the journey, man! Savor every step!

which one

L.Adamson said:

A 9(a) with a two axis A/P and constant speed prop will make a great flying airplane. Wouldn't want one without them! It was a 9a that finally spoiled me with it's auto-pilot system, after a series of long cross-country's.

And the C/S does wonders for getting it down quickly, when desired, not to mention a whole lot better for high altitude airports.

L.Adamson

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no doubt about that but
which one would you rather fly imc w/o auto pilot..wasnt saying it couldnt benefit from it just that the 6,7,8s benefit more from it.IMHO

I agonized over this question too, and ended up with the -7A. I've been flying only a few years (since 2002), and have only now started to settle in to a routine for the kind of flying I do. It's a mix. I fly to Utah for work, Yellowstone and Montana for vacations, and I fly with the local Lunchwaffe for those $100 cheeseburgers on the weekends. I have a 182 now, and rent a Super Decathlon when I want to go upside down. I am developing a real love for aerobatics, so that's another factor.

All in all, I can't speak for anyone else, so I can only offer my rationale. The following are the primary reasons (in order) of why I opted for the -7A:

• Light aerobatic capabilities
• Greater margins for g loads (nice for mountain turbulence encounters)
• Could take a higher horsepower engine (again, nice for the mountains)
• Slightly higher useful load
• I find the -7A to be plenty stable

I think the advice you were offered to finish up the flying lessons and settle into a routine before building is good advice, but there is probably nothing wrong with getting rolling on an RV too. I don't necessarily agree that building and flying are mutually exclusive. You just have to strike the right balance.

Cheers,
Dave

9A? What's that? I didn't consider anything that wasn't aerobatic. The first time I went upside down was exciting. I know, aerobatics aren't for everyone but, for some, they are everything.

For me, the decision was between th 7 or 8 series.

Have fun. This part of your build is pure fantasy.

Jekyll
7A

Only by writing down what you want from a plane will you figure out which RV is best for you. If acro is in the list, go with the -7, if not, go with the -9.

The argument that the -9 is weaker and the -7 stronger doesn't really fly, IMHO. How many of you flew Cessnas and Pipers and never gave the strength of those planes a thought? Well, the -9 is just as strong as all the other certified airplanes and probably stronger.

As for the higher useful load, I call BS on that. If you add a bigger engine, which everyone seems to want, you cut right into that useful load. Now add a CS prop and that number goes down even further. Remember, higher GW doesn't necessarily translate into higher useful load.

The average empty weight of a -7A (according to Dan's site) is 1116 lbs, this translates into a useful load of 684 lbs. (1800 lbs GW)

The average empty weight of a -9A (same source) is 1085, and this translates into a useful load of 665 lbs. (1750 lbs GW)

Now when you fill the tanks things change.
Put 42 US gallons in the -7A and you now have a useful load of 432 lbs
Put 36 US gallons in the -9A and you are left with 449 lbs.

The truth is, the numbers are too close to really matter.

I love acro but my wife and I love backpacking even more and we hope to use the -9 to extend that to some out of the way places AND she might like to learn to fly some time so the -9, with its lower stall and "slower" handling was the best choice for us.

The trick is to find out what the best choice is for you.

Good luck with making up your mind.

Yes you can!

I chose a 9a. Started building 14 months ago. finished my private pilots lisence the first two months of building then started my IFR ticket. Got the IFR ticket two days ago and plan to finish the 9A by end of Nov.

It can be done, but you need an understanding wife and a little extra time off from work!!!

Duane

David Johnson said:

I don't necessarily agree that building and flying are mutually exclusive. You just have to strike the right balance.

Cheers,
Dave

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i second this. i was building 11 months before i was flying. got my ppsel in 5-6 months. 40 something hrs. toook a year off, not by choice. and now i am building and flying again..sometimes when i am tired of building i go fly..one serves the other.. i am now up to around 80 hrs hope to have many more before the 7a is ready. then i'll go see alex or mike. JMHO

The argument that the -9 is weaker and the -7 stronger doesn't really fly, IMHO. How many of you flew Cessnas and Pipers and never gave the strength of those planes a thought?

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I thought about it a lot before I bought my 182. The strut wing Cessnas are among the sturdiest aircraft in the sky, with an exceptional record for structural integrity. The 172 has had only 2 in-flight breakups that I'm aware of in over 40,000 aircraft, subjected to all sorts of abuse. One of these was chalked up to pilot incapacitation, and the other was still being investigated last time I looked. My point is, structural strength was one of my primary selection criteria when airplane shopping, and remains so today.

Well, the -9 is just as strong as all the other certified airplanes and probably stronger.

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There isn't any data on this that I'm aware of. We do know that the RV-7 structure is stonger, and that's a margin that's important to me. Ever been thrown around by a rotor?

Dave

David Johnson said:

I thought about it a lot before I bought my 182. The strut wing Cessnas are among the sturdiest aircraft in the sky, with an exceptional record for structural integrity. The 172 has had only 2 in-flight breakups that I'm aware of in over 40,000 aircraft, subjected to all sorts of abuse. One of these was chalked up to pilot incapacitation, and the other was still being investigated last time I looked. My point is, structural strength was one of my primary selection criteria when airplane shopping, and remains so today.

N941WR said:

Well, the -9 is just as strong as all the other certified airplanes and probably stronger.

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There isn't any data on this that I'm aware of. We do know that the RV-7 structure is stonger, and that's a margin that's important to me. Ever been thrown around by a rotor?

Dave

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Dave,

You made me curious so I checked my builder's manual, since I couldn't find it on Vans' site.

At a GW of 1600 lbs the RV-6, -7, & -8 are designed for +6 and -4 G's.
The RV-9 at the same 1600 lbs GW is designed for +4.4 and -1.8 G's.

According to the 1985 C-152 manual (Sorry, don't have the C-172 manual handy.) I have in front of me, that plane was designed for 4.4+ and 1.76- G's. The manual goes on to say:

1985 C-152 Manual said:

The design load factors are 150% of the above, and in all cases, the structure meets or exceeds design loads.

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Vans will state the same thing about their load limits.

Bill,
One minor correction: The aerobatic gross for the -6 is rated at 1375 lbs.
Yes, It is stronger than that, but that's the designated load limit.

Bill,

Thank you for pulling the data from the sources that you have, I do not dispute that this is what the manufacturers have published. These numbers represent that they have engineered the airframe to meet the requirements of standard category aircraft certification. However, that does not consider operational history, which provides much more insight into the relative strength of the aircraft structure in service.

I don't have the data handy (wife is waiting on me to go to breakfast), but the in-flight breakup rate is not the same for all aircraft, even though they were designed to the same minimum standards. There are several reasons for this that include (but are not limited to) typical flight mission, manufacturing variances, inadequate consideration for the effects of metal fatigue, and inadequate margins for flight regimes other than direct, linear airframe loads. In general, there is significant data to suggest that some designs are inherently stronger than others in day-to-day operations despite being tested to the same standard, which is why we've seen ADs on Commander wing spars, Bonanza V-Tails, and so on.

With that in mind, in the experimental world, we don't necessarily have the same level of service history data- particularly on newer designs such as the RV-9 or even the -7 that we do with 40-50 year old designs. The -9 may prove stronger than its cousins certified in the standard category as service history bears itself out, or it may not. It seems prudent then to consider that because the -7 has been designed to withstand greater airframe loads, that the additional margins built in provide a cushion for what we don't yet know about the service history of the structures. Make sense?

Just trying to illuminate some additional key points to consider...I'm not trying to change anyone's mind or judge which airplane is better. I can only say that for me, the manufacturer's published numbers only tell part of the story.

Dave

David-

Although I agree with Bill, I see what you're saying about not having any realworld data to argue whether the -9 is "strong enough" compared to your Cessna. (I too have flown a 182 a lot, so I know what you're saying when you like seeing those struts out there under the wing, even if it may just be psychological).

However, you seem to be zeroing in on one aspect of safety that, in reality, is the least likely aspect you need to be worried about. When's the last time you hit turbulence that exceeded 4.4g? I've hit some bone-jarring bumps that I swore must have been 6-7g. After I looked out at the wings to see if they were still attached, what did the meter say? Less than 2.0. If one were likely to hit turbulence that was capable of breaking the airframe, I would blame that (in MOST cases) on the pilot's poor pre-flighting and decision-making, not the airframe. Van's has no record of airframes breaking up because of turbulence. The relatively few structural issues seem to have been pilot-induced. I would doubt that the -9 would fare any worse.

We all look at choices differently, but I too was very interested in issues of safety. Consider the following (all numbers taken from the cafefoundation.org testing reports):

Stall speed: about 10% less on the -9. Since the short-wing versions stall pretty slow to begin with, this may seem like no big deal. However, survivability in an impact does not vary in a straight line with speed. Any decrease in speed will exponentially increase survivability. So that 10% drop in speed probably means something more than a 10% greater rate of survivability. (I saw a chart on this once--if anybody knows where it is I'd love to have a copy). Thus, those 7mph difference between the 9 and it's short-wing cousins may mean something in terms of real life survivability.

Glide ratio: For the 9 it is 12:1. For the short wing versions 9:1. If you have an engine out would you like to be able to glide 33% farther?

Sink rate: For the 9 it is about 600fpm. For the short-wing versions at least 1000fpm (on a good day). That means in the -9 you have almost twice the amount of time to troubleshoot problems.

Again, these were only the factors that informed my decision given the type of flying I do and where I do it. Others may be more concerned about other factors, and that's fine, but I think it's important to focus on those possibilities that are most likely. Is engine trouble or fuel starvation more likely than airframe-breaking turbulence? I think accident reports would bear this out.

Just my thoughts (and my signature suggests a built-in bias) .

A humble opinion

Safety is an important consideration for me also, so I first looked to see what factors lead to accidents. While the raw NTSB reports are online, the Nall Report (http://www.aopa.org/asf/publications/nall.html) seems to do a reasonable job of categorizing the causes of aviation accidents. In 2004, the Nall Report attributed 75% of all accidents (and over 78% of all fatal accidents) to the pilot. It attributed only 10% of fatal accidents to mechanical or maintenance issues.

Of the pilot attributed accidents, maneuvering (22.8%), weather (19.7%) and takeoff/climb (15.8%) account for well over half the fatal accidents. Obviously better pilot training pays the most dividends toward safe flight. And when considering aircraft, any aircraft characteristic that makes it easier and safer for the pilot to maneuver or takeoff should be accorded priority when choosing between different models.

The RV-9A is lauded for its "docile" handling characteristics and having lower stall speeds than other RVs. So the only RV that seems to have been designed with characteristics that seem to address the most common causal element of accidents is in fact the RV-9A. Airframe structural failure simply doesn't rate high as a consideration on the priority list.

And to date, I can only find one fatal 7A accident no fatal 9A accidents - though the fleet sizes are not comparable. (And the 7A accident was sadly among the second leading causes of accidents - weather. See http://www.ntsb.gov/ntsb/brief.asp?ev_id=20031222X02074&key=1 )

By the way, among non-fatal accidents attributed to pilots, a whopping 39.8% are during landing. So any plane that makes landing easier should rate high on the priorities of those who consider safety important (or at least safety to the wallet). I think this means favoring the craft with lower stall speed, provides good control surface authority at low speeds, and have a nose wheel. Again, the 9A seems to have the edge over the other RVs.

So in my humble opinion, all these factors indicate to me that the 9A would, under identical circumstances, be a safer choice than the 7A.

However, you seem to be zeroing in on one aspect of safety that, in reality, is the least likely aspect you need to be worried about.

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Steve-

Thanks for your thoughts. I don't dispute any of your points. I agree with you that there are several other factors of greater risk to safety than the airframe itself. We were discussing the relative merits of the 9 vs. the 7 or the other way around, and I listed what my considerations were in choosing the 7. Among them were the added structural margins. Others then chose to call this out and I was responding to their points. Thus the appearance that I was "harping" on this one issue, when in fact I consider it as but one of many factors.

Structural integrity has special meaning for me because I spend a lot of my time over the Rockies. When the winds get rolling, the chances of a severe turbulence encounter go up. Last year a T210 went down in southwestern Colorado after an encounter with severe to extreme mechanical turbulence. The added structural integrity of the RV-7 is a benefit for me. As I said before, I can't speak for anyone else.

Cheers,
Dave

David Johnson said:

Structural integrity has special meaning for me because I spend a lot of my time over the Rockies. When the winds get rolling, the chances of a severe turbulence encounter go up.

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Yes, that's one of the bummers about living right up against (and on the leeward side) of some fantastic geography isn't it! Ellensburg, WA is just east of the crest of the Cascades. Beautiful flying, but it can be pretty bumpy when the winds blow (20-30kts not uncommon and I see occasional rotor clouds)! It does remind me a lot of when I lived on the front range of CO. Wouldn't trade it (living in either of these two places) for the world though.

Happy building.

Turbulance? They have a V speed for that

N941WR said:

At a GW of 1600 lbs the RV-6, -7, & -8 are designed for +6 and -4 G's.
The RV-9 at the same 1600 lbs GW is designed for +4.4 and -1.8 G's.

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There is one big problem with the above statement.

Published limits and design limits are not the same thing and those numbers are published limits. When you hear Van talk about aerobatics in the 9 he's quite careful with his words. He says that the 9 was not intended for aerobatics or it was not designed with aerobatics in mind. I asked him about the ultimate strength of the wing, he just smiled and said it was designed for the utility catagory (+4.4, -1.8) and would not comment on any numbers.

One might ask why would a company publish a limit lower than it was designed to. Marketing is one reason they do this and I believe that is what Van's is doing. If you want to create a precieved difference in two or more or your products that are actually very similar you would publish specs that make them seem quite a bit different. We do this in the auto industry all the time. An example of this is to derate a 3/4 ton truck so that it seems like there is actually a difference in the 3/4 and 1 ton trucks. Now you've taking one truck a created two markets.

In converting my 9A to a 9 I came across quite a bit of prejudice against the RV9 from Vans. They are very clearly trying to push the 9/9A in a different direction than the 7/7A. The RV9A was to be a trainer so it should be built as a nose wheel because that fits the trainer perception better. The poeple that have 9's now what I'm talking about.

I'm making no claim about the strength of the 9 wing or that poeple should disregaurd the published specs. But as far as I know Van's has not published actual test data between the RV7 wing and the RV9 wing.

One last thing, if you are concerned about turbulance, they have a V speed for that.

Thanks for all the replies it has really been a learning experience!

What about resale value? What happens if after I build my 9A or 7A I want to sell it because ... I want to build a 10

Which airplane (assuming similar configurations) would have more demand? Would be easier to sell?

7 vs. 9 is a simple decision: Build the 7 for aerobatics; otherwise build the 9. If you talk to the factory folks, they ALL prefer the 9 for X-C.

Van's has sold a lot more 7 kits than 9's although 9 sales seem to have picked up, according to an employee I talked with @ the homecoming. They feel that as more folks get rides in 9's, sales will pick up some more. FWIW, in our EAA chapter, all RV's that have been started in the last 3 years have been 9's. We have one builder who is pretending to build an 8 (got the kit several years ago, has about 10 hours into the project & swears he will build it, but he is in his late 60's).

The 7 is more responsive which can be both good and bad. The handling is fun, it makes you want to yank & bank. But for traveling, you have to pay attention more, especially in pitch.

To me, the decision is not which to build, but do I want to do aerobatics? You make that decision, you have your answer.

Resale value: Probably more dependent on workmanship, salesmanship & how pretty it looks than on which model it is, at least as far as 7's & 9's are concerned. I was surprised to see an ad recently for a -9 for $121K. Doesn't mean it will sell for anywhere near that amount, of course. I haven't done a systematic check of prices, but it appears that 8's go for the most (well, not counting the 10), 3's & 4's the least ( and note the 3's & 4's take the most work, so they have to be a labor of love).

I'm doing a 9, but it took a lot of soul searching to admit I would probably never really do aerobatics.

N916K said:

One last thing, if you are concerned about turbulance, they have a V speed for that.

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And Va in the -7 would be much higher than the -9 (a function of stall speed and load limits).

A really good discussion on RV-7 vs RV-9A.

Everything I have read in this thread so far is the same stuff I thought about when making the decision in Van's exhibit booth at Oshkosh 2002. The end result is my flying RV-9A which came in at 1,184 pounds with O-320, C/S prop, interior, paint, and CD/Tape player entertainment system. When I went through the weight and balance issues, I realized I could placard the airplane with two sets of V-speeds. One set of numbers for the usual way I fly the airplane. Those numbers are the suggested numbers published by Van's. The other set is for the maximum gross weight which will not exceed the CG limits with a typical load when going camping with a friend in the right seat. That max gross weight is 2,000 pounds. The DAR I used had done a number of RV's before he got to mine. My airplane was the 300th (of all airplane types) he had certified for flight. He looked at all my documents, the 2,000-pound weight limit, the V-speed limitations for that weight, and agreed.

I realized long ago that aerobatics were not for me during spin-recovery training in a 152. The RV-9A was the right choice for me. With more than 200 hours on the Hobb's meter and many cross-country flights to different regions of the country, it is still the right choice for me!

I have recently equipped the airplane with a video camera system that allows all the radio and intercom audio in the airplane to go onto the video tape. You can sample the most recent videos I made going into and out of Oshkosh 2006 on my web site at www.n2prise.org.

As far as converting an RV-9A to an RV-9, I would not think of it. I read a story on the Tennessee Valley RV Builder's Group web site that spoke volumes about AFT CG limits and tail draggers. Read this article for the details: http://home.hiwaay.net/~sbuc/tvrvbg/west_trip.html.

When you load a nose-wheel airplane too heavily in the cargo area behind the seats, the balance on the landing gear is obvious when you step on the airplane before you start the engine. With a tail dragger, if you did not do the weight and balance correctly, you won't know about the AFT CG until the wheels lift off the runway. At that time, it might be too late if the AFT load is too heavy.

Jerry K. Thorne
East Ridge, TN
RV-9A N2PZ "Enterprise"