Hi all, new member, 7 vs. 9

Hi all. New member here. I'm interested in building an RV-7A or 9A, haven't decided which yet. Mission is wife and I go to visit grand kids 1,000 miles away about 4 times a year, and $100 hamburger type Sunday excursions in between. Mostly grass fields both at home and at the hamburger locations. The plane would be IFR configured.

I like the 500 fpm glide capability and low stall speed of the 9A, and with a 160 hp 320 on both the 7A and 9A, performance is just about identical between the two, except for the stall speeds and G handling. No interest in aerobatics, but would like to know that in an emergency, if I needed to stress the plane, it wouldn't break.

Here's a question that'll probably get me some flak. Has anyone installed an air conditioner in their RV? I'd be very interested in an automobile type environmental system with auto temperature control, etc. I know it's extra weight, but I'd trade some performance for comfort. Feasible?

I called Vans when I had the same question, They put me through to Ken Kruegar. What it basically boiled down to was what do you was do you want to do aerobatics or do you want a stable cross country machine. I would love to do aerobatics every once in awhile, but I'd much rather take 3 day weekends once a month and go somewhere far away.

I'm taking the 9a myself, its not that much slower than the 7 and burns less fuel since its got a smaller engine. (Assuming your going for the 360.)

My 2 cents. Call Vans...

Jeff

Natural air conditioning...

Just climb above the cloud layer and it gets cool enough. If you really insist on A/C for ground ops, you could have a problem with where to put the compressor and a belt drive for it without a custom cowl design. And then there is the weight of the compressor and the FAN to circulate the air through the evaporator inside the cabin. Plus, you will need more insulation to give the A/C a chance to do the cooling thing. Then last of all, you will really need to seal the cabin for air leaks to keep that cool air inside.

As far as the choice of the RV-9A over the RV-7(A), I chose the 9A for the lower landing speeds due to the longer wing span. It climbs faster than the 200 HP RV-6's, 7's, and 8's due to the lower span loading of the 9. The 9 has a 28-foot wing span, while the others check in at 23 feet.

The lower landing speed of the 9 will minimize the chance of breaking it. As for G-forces, it compares to a Cessna 172, not a Laser 300, Pitts, etc.

Jerry K. Thorne
RV-9A N2PZ

n2prise said:

The 9 has a 28-foot wing span, while the others check in at 23 feet.

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Nope, the -7 has a 25' wingspan.

23' is the -8, as it has a narrower fuse.

If you wanna yank and bank, get the -7.

If you wanna cruise and look at the pretty leaves, get the -9.

Either way, you will be pleased!

CJ

I haven't yet heard from anyone actually flying the -7 that it isn't a good Xcountry machine (you there, Roberta?) compared to the -9. The fuselages of the -7 and -9 are identical so ergonomic comfort is certainly the same between the two.

It seems to me that I wouldn't want to fly long Xcountry with either the -7 or -9 without an autopilot, and that with one, you wouldn't notice any difference other than than that you'd cover more ground faster in the -7.
Then, the only difference is that when you turn off the AP in the -7, you can let the fun begin.

The reason that an A/P is mandatory, in my opinion, is that I confess that in the few longer Xcountry's I've done in a 172 (without autopilot) that I would occasionally let my heading and altitude wander (just a wee bit) when I was busy with other things. Anyone who denies that they've done the same is either lying or has flown captain on the Space Shuttle.

One more thing as to why I went with the -7; I have personally been hit so hard with shear that I could see the wings move on the 152 I was in, and I was truly concerned that the darn things might break. I'm talking about the kind of shear where loose objects dented the ceiling panel.
Even though I'm not big into airbatics, I rather like the idea of my Xcountry aircraft being able to withstand potential momentary stresses of cosmic forces.

It appears that the only significant advantage to the -9 is it's slower stall speed due to the Roncs airfoil, so if that's a big issue, then one would have to go with the -9.
For perspective, though, the stall speed of the -7 is only 4mph higher than a 172 w/full flaps, while the -9's stall speed is the same as a 152 w/full flaps. I've flown both, and I can't recall much "felt" difference at all in how they handle on landing.

Either way, you still spell fun; "RV".

Just thinkin' out loud.

n2prise said:

As far as the choice of the RV-9A over the RV-7(A), I chose the 9A for the lower landing speeds due to the longer wing span. It climbs faster than the 200 HP RV-6's, 7's, and 8's due to the lower span loading of the 9. The 9 has a 28-foot wing span, while the others check in at 23 feet.

The lower landing speed of the 9 will minimize the chance of breaking it. As for G-forces, it compares to a Cessna 172, not a Laser 300, Pitts, etc.

Jerry K. Thorne
RV-9A N2PZ

Click to expand...

As to climbing faster, I'm not so sure about that. The spec's from Van's website, list the 6,7, and 8 as all climbing faster at solo & gross weights with the 180/200 HP engine combo's, versus 160HP for the 9.

Without doubt, the 9A lands at a slower speed. Throttle off over the threashold seems to work everytime.

Since I once paid for aerobatic instruction in a Pitt's S2B for a couple of years, I still lean towards mild aerobatics. Just completing a 6A, since 7,8's, and 9's were not available at the time.

L.Adamson --- RV6A,180HP,C/Sprop

Air Conditioning

If you don't mind having a 28 quart coleman cooler in your airplane, you can buy a $50 airconditioner to attach to the lid. Do a search for Coleman or coolaire or portable coleman air conditioner, etc. It's supposed to work with battery or off your power plug. Never heard of anyone using it in an RV, but it might work.

Sounds like air conditioning is somewhat impractical...

Is it common/possible to fly with slider canopies open? I've searched and haven't found mention of it. Many years ago while doing summertime touch and go's, we would open a side window on our KC-135A's (no air conditioning either). Very windy and nav's would get a bit upset with charts flying around everywhere, but it did cool things down.

mission?

If you start flying with other RVs you will be a drag if you can not keep up.
I have no 9 experience, BUT, I have flown a 150 hp and a 160 hp RV 8, and RV8a with my group of BCs and it is not fun not being able to keep up with every one.
If yours is a solo mission slow is ok.

Supprised?

someone didn't jump on me for this one?
My RV8 160 hp, now owned by Rick Freeman, N82RV, is just as fast as the 180 HP RVs Turbo, Krash, Scorch, and others fly, but the clime out and catch up rate is slower for him. He has to run at 2500 rpm to do what we 180 constant speed guys do. and he burns more gas too. Solo he uses less because he is not trying to keep up.
Guys, I'm still trying to figure all this out. We just do not have any 9s flying with us.
I figure that when this happens, Gary, we will have to pull back more, ?

One guys experience

I have flown 6A's and 9A's. Currently buiding a 7A. In the 6 we set up around 23 square and the 9 has to run at full tilt. These three planes that I am lucky enough to fly in on a fairly regular basis are all very similar. They all have 180 HP 360's with constant speed and the 9 just can't keep up.

It is, however, a RV and very nice to fly. It seems to have a bumpier ride and is less responsive on the controls. I am a low time pilot but I find that the 6's are not difficult to fly especially when you get used to the rate at which things happen.

They say that the 6 is very similar to the 7 and for my money the 7 is the only road.

9A all the way

I have flown both the 6A and 9A. Sink rate in the 6A is significant. Don't get me wrong, it's not difficult to land the 6A, just different, it comes down when you pull the power. Since I haven't flown the 7A, I guess I can't verify the landing behavior. The 9A takes some practice to get it to come DOWN. Ask any 9A pilot. Also, not difficult, just different. I like the lower sink rate, the longer wings, and the cruise performance. I don't want to go upside down. If you compare the 7A with a 200hp, to a 160hp 9A on a 600 mile trip, the 7A will get you to your destination 15 to 20 minutes sooner than the 9A (using Vans cruise numbers). Lots of factors to consider for that 15 minutes, not the least of which is $$. 9A all the way for me. I guess we all love the Vans airplane we end up building. You really can't go wrong. Jack

Jaypratt said:

I figure that when this happens, Gary, we will have to pull back more, ?

Click to expand...

That's a good point, Jay! I'll just have to depart a little before you guys ....or convince you fella's to throttle back for the new kid on the block

I'll just have to depart a little before you guys ....or convince you fella's to throttle back for the new kid on the block [/QUOTE]

Gary,
Thats the rub. If you leave before everyone you will be a solo.
We have a lot of fun with each other flying in a group. Besides, who will tell the world on 122.75 when you do something dumb??, if we cant see it happen???
Some of us have practiced formation, and do that on our trips. The 160 hp guys do take off first but they are running harder.

Can we quantify the issue?

So what are the real word approximate numbers that we are talking about here? I mean, how much of a real problem is it?

Obviously the climb in a 180hp-8 will be better than in a 160hp-9, but that lasts about 10 to 15 minutes. What about in cruise?

Is it a case in which the 160hp-9 running at 100% power can't keep up with the 180hp-8 cruising at 55% power? Or is it more like the 160hp-9 needs to run at 60%-75% power to keep up with the 180hp-8s cruising at 55%?

According to Vans performance numbers, the 180hp-8s cruise at about 182mph at 55% while the 160hp-9s cruise at about 169mph at 55% and 189mph at 75%. It seems like the 8 guys should be able to cruise nicely at 55% while the 9 guys run about 70% to keep up.

I am not saying it isn't an issue, and yes nobody ever complained about having too much power. But is it a show stopper that excludes the 9 guys from the formation club or is it more of a bragging rights thing?

Maybe there are other things that I am missing. If so, please explain.

Thanks!

I hope RV pilots really aren't this bad

Thanks Tom

People keep going on about this plane being faster than that plane. As far as RV's go it matters more what engine is in the plane than what model it is. A 160hp RV is not as fast as a 200 hp RV. Wow, really???

My RV9A with a slider, which has all the problems a plane could have if you listen to the RV snobs, has the same top speed as a friend's RV4. The RV4 has the same engine and prop as mine.

So I'm going to keep having a blast flying my 9A, even though it only goes 190 mph.

I'd hate to see what would happen if someone with a Cessna 150 pulled up to the pumps while an RV was there. They'd probably get stoned and the tires on their Cessna slashed.

Tom,

I think they may fly some formations inverted, or something

Otherwise, us "-9 drivers" should be able to do OK with them. If the speed difference is a huge factor, I'll offer to buy them lunch if they run at 55% (or whatever) while I buzz along at 70% (or however the numbers work out)

In any case? It will be fun! And if Doug and Jay and others beat us -9 drivers somewhere? I bet Doug is sitting there getting some nice photos of us on final approach!

not a show stopper

The 0-320 engine with a constant speed prop does about the same here in Dallas. On reaching about 5000 ft or so the thing acts like you pulled the throttle back. The 0-360 really shines over 5000 ft.
Larry Vetterman used to work for the Goverment and opperated fleets of Super Cubs. His policy was to put a 0-360 in any plane based at or over 5000ft.
I don't know all the reasons, but flying the 0-320 constant speed,RV8A I built here could not keep up with some of my buds on trips. I had to ask them to pull back, alot. It is interesting that we used the same amount gas on one trip to New Mexico and return. To the tenth of a gallon! He said he was runing under 20 inches of manifold. His was loffing and mine was 25 Sqrd.
I have noticed on some of the Home Coming Trips we usualy break the group into flights of 4. It is a waste of time to arrive somewhere with 16 RVs all wanting gas at the same time. We usually put like engines and props together. Some times when possiable we head to two different airports to spread out the gas wait.
On formation, lead flys at 140 kns so everyone has some throttle left.
Again, I have no RV9 experence. Freeman, RV8 160 hp, is just as fast in cruse as the rest of the fleet . But had trouble on the homecoming trip two years ago. A lot of the stops are high alt. I expect the 9/9a will do fine.
The start of this thread asked 7? or 9? My point is the 180 hp RV planes fly the same. If your mission is solo mostly. The engine is not important. But if you start to fly with a group think of what they fly behind. It is a huge difference in the two engins.
I just hope my buds do not get 200 hp engins

Thanks all. Very informative.

Is it possible/practical to fly with a slider canopy open (in case of smoke, or to cool the cockpit down at low altitudes)?

Open canopy

I don't believe it is recommended to fly with an open canopy as the canopy ieself is a lifting surface. Check with Vans on this. I had occasion to have a partially open canopy (Don't ask why) and the wind noise was horrendous even with noise cancelling headsets.
At Sun and Fun I happened to overhear a conversation with Ken Kreuger and a potential customer as to what Vans model was the best. The answer was that when it came to flying to the show everyone wanted to fly the 9. I have flown a 6, 6A, 7 and 9A and I find that all are wonderful aircraft. As you move up the number scale the stick forces become progressively heavier but still all the planes fly RV style. I did notice that when I entered a steep bank of 65 degress with the 9 that I didn't have to use hardly any back pressure to maintain altitude. It was like the plane was on rails. If most of the aerobatic manuveurs you are planning only include a roll or loop and are done properly, you could easily do them in a 9. Other than that, go with a lower model number. Also, when it comes to speed, all things considered, comparing engine sizes is apples to oranges. My old 6 was faster in the Sun 100 race with an 0320 and fixed pitch prop than many planes that had an 0360 on them. The key is a clean airplane with no drag. I plan to build a 9 eliminating external steps, and antennas. I have seen it proven time and time again how much drag those little items provide.

A comment in another thread makes me wonder whether the 7 or 9 would be better for short soft field landings and takeoffs. Any comments?

Im also curious what effect a larger engine (200 hp range, same as 7) would have in a 9- good or bad?

The best RV

Van was asked at Oshkosh what the best RV was, RV -4, -6, -7, -8? He said without a doubt, the RV-3. Ouch From many a stand point, I can see what he means. I have flown the -4, -6 and now building a RV-7. They all fly nice. Build it light, clean and have fun. As far as speed, fuel economy, aerobatics it is up to you. I think most people think, at least I do, the RV-9 is less "hot". What does that mean? Van calls it more "relaxed". The RV-9 has a lower stall speed for one.

I think people have and continue to get into problems with RV's because they don't fly them at proper speed and do get into higher sink rates. Why? (experience, currency) The RV-X is not hard to land if you fly it on the numbers. I have almost 1000 hours in RVs (all tail draggers). They are easy to land. Is the RV-9 impervious to landing problems? No, you can still stall it or land hard, bounce or loose directional control with a -9, as much as any RV, no doubt, but it may be just a little easier to land. For many pilots that is a factor. Nothing wrong with that.

The -9 is basically a -7 fuselage with a different wing and stab. It has more wing area and was the first time Van departed from using the tried-n-true NACA 23013.5 airfoil he always used. This NACA airfoil goes way back, is one of the best around, used in countless famous well regarded past airplanes and continues to kick the butt of many newer Johnny come lately fancy airfoils. In the 80's laminar flow and GA airfoils were suppose to be like magic, with huge gains in performance; they looked good in the wind tunnel, but they did not deliver in the real word. Well the airfoil on the RV-9 is obviously doing its job, at least within this power loading, wing area, wing loading, span and aspect ratio. Clearly it has low drag in cruise, low stall speed and I am guessing a docile stall characteristic. Not a leap in performance but a tweak, for spacific reasons. Nuff said. What about the NACA 23013.5 airfoil? Well RVs are one of the most popular homebuilts with thousands flying, with wonderful handling qualities, that fly fast but still have low stall speed. Nuff Said. They are all good, but there is no free lunch. Notice the RV-9s new airfoil top speed about is about 5mph slower than the RV-7 (160HP), which is the about the same differnce in stall speed, 44 mph vs. 51 mph. Again no free lunch, gain low end loose top end.

In light airplane designs there are compromises and all RVs have a good balance. You can tweak it a little one way or another but there is no quantum leap. That is what Van did, tweak. Why carry a 9 g spar around in an airplane that is only going to do straight and level. Why have less wing area, when a little more will get lower stall at with only a small loss of top end (with a new airfoil)? Van has tweaked the airframe, not redesigned it. A RV-9 is a RV, Nuff said.

Most of these debates come from a builders choice, who wants or needs the advantage one design has over another, like slider vs tip up, but they do not want to admit or accept the compramise of that design. No need to justify a decision, its all win-win. If you are not a hot acro / formation pilot or feel with your experience the RV-9 is a better match, than build that and don't worry about justifying the 5 mph at the top end, or the lower "G" limit. Who cares. If that is the way you fly; the RV-9 is more optimal for you. I like to do acro, formation flying and enjoy racing on occasion, so the RV-7 was my choice.

I liked the RV-6 and could have got one of the last QBs, but liked the RV-7 fuel, pre-punched parts and higher gross. Did not go RV-8 because I was tired of the tandam seating; on a long XC you can sperad out more if solo, and with a pax it is more fun to see the person you are talking to, IMHO.
(justification in progress )

If I had a choice I would have 8000 sq ft hanger with a Pitts (or other hot acro plane), a Cessna Citation, a Turbine Beaver or Caravan on floats, a Super Cub on Tundra tires and a few RVs (-3, -8, -7, -10). Oh well, I guess I'll have to get by with one 180HP RV 7 and a small T-hanger.

George RV-4, building RV-7