[SlowJoe]

I am a student pilot, and am hoping to order a tail kit soon. I've read pretty much every thread on the 7 vs 9 question. But I still can't make up my mind. Since I am very low time, there are some things about the nine that appeal to me. However, by the time I get her built, I'm sure I will be much more experienced as a pilot.

My question is how the 7 and 9 compare to the DA 20 I am training in. In the pattern, I pitch for 80 and put in the first notch of flaps. After I turn final, I pitch for 75 and put in the final notch of flaps and maintain this speed until I flare for landing.

How does this compare to the speeds for the 7 and 9? I know the 9 has a lower stall speed, but what I want to know is what do you fly your approaches at. Is the 7 a lot "hotter"?

Also, I've heard people say the DA 20 is like a glider. How does it compare to the wing on the 9. People say the 9 "floats" a bit. Is it similar to the Diamond?

Finally, will the 9 with a 360 keep up in cruise with the 7's with 360's?

Thanks

Joe

 

[n5lp]

I am a student pilot, and am hoping to order a tail kit soon. I've read pretty much every thread on the 7 vs 9 question. But I still can't make up my mind. Since I am very low time, there are some things about the nine that appeal to me. However, by the time I get her built, I'm sure I will be much more experienced as a pilot.

My question is how the 7 and 9 compare to the DA 20 I am training in. In the pattern, I pitch for 80 and put in the first notch of flaps. After I turn final, I pitch for 75 and put in the final notch of flaps and maintain this speed until I flare for landing.

How does this compare to the speeds for the 7 and 9? I know the 9 has a lower stall speed, but what I want to know is what do you fly your approaches at. Is the 7 a lot "hotter"?

You talk about your speeds but give no units. The only DA20 I have flown had an airspeed indicator that showed knots. If that is what you are using, it sounds like you are flying final at far faster speeds than any RV would typically use. I have an RV-6 and fly final at 60 to 65 knots depending on weight and gustiness. An RV-9 would typically use a speed around 5 knots slower.

Also, I've heard people say the DA 20 is like a glider. How does it compare to the wing on the 9. People say the 9 "floats" a bit. Is it similar to the Diamond?

The DA20 glides much better than a 6 or 7 and better than a 9 also. It has a much higher aspect ratio wing. It has been my experience that the RVs and the DA20 do not float if the proper speeds are used. If you are fast, the DA20 is less forgiving of that than the RVs would be, particularly an RV with a constant speed prop. A constant speed prop has a large braking action that lets the airplane decelerate quickly even when an excessive approach speed is used.

Finally, will the 9 with a 360 keep up in cruise with the 7's with 360's?

Everything else being equal, no, but the difference is not huge.

 

[N941WR]

I am a student pilot, and am hoping to order a tail kit soon.

Great! Build the -9. It will take you a number of years to complete and if you are like most pilots, you won't have time or money to fly while building.

Once you have it done, get current, fly the -9 for a few years and then, if you want to do acro, sell the -9 and build a -7 (or -8, or -4, or -3).

Everything else being equal, no, but the difference is not huge.

It depends at what altitude you are flying. The higher you go, the more efficient the -9 is. Again, the difference is not huge.

Also, the -9 will jump off the ground but and this is big BUT, if you build a heavy airplane, be it a -7 or a -9, all bets are off on all performance measures.

Get a ride in both, don't make up your mind based on something you read on the net. This is a costly decision; make the right one up front.[/quote]

 

[Greg Arehart]

I've rarely had an issue with float on the 9, though it certainly does not sink quite as fast as a 6 or 7. Generally the 9 is slightly slower than the 7, but not by much. And it depends on altitude and prop pitch. I can get right at 200 mph out of my 9 (burning a lot of fuel) and easily cruise at 165-175 mph true on 6-8 gph (depending on altitude). I have FP prop pitched for cruise, since that's where I spend most of my time. The 9 is also a bit less twitchy than the 6 or 7 (i.e., feels a bit more stable) IMO.

I agree, try to get a ride in both and maybe a half hour or more of stick time to see the difference. It is very much a personal decision.

cheers,
greg

 

[JDRhodes]

Student pilots can get all uptight about getting a permanant airplane that is "most like the xxxx-trainer that I've been flying."

Really, I doubt you WANT something that flies like a trainer. None of the RVs are at all difficult to fly. I wouldn't factor your training airplane's characteristics into the equation. Get waht you want for the reasons you want it. Get some transition training, and you'll be fine whatever you pick.

 

[Andy Hill]

In practice RV-7 and -9 do not differ greatly.

However, if you have not decided between the 2 and ask:

Finally, will the 9 with a 360 keep up in cruise with the 7's with 360's?

why conisder a 360? And go directly against the manufacturers' recommendations?

If speed / can I keep up are so high in your priorities then build the one designed for that. Are you really sure at your stage you do not wish to fly, or even try, aerobatics / tailchasing? Build a 9 and you are committed to that...

In short, IMHO the 9 is great for those who know what want, and more importantly what they do not want. Unless you are in that situation, I would build the 7 - well, no I would build an 8 (again ) - it is an "all rounder" and the 9 only beats it in the 9's special areas to a small degree.

Andy & Ellie Hill
RV-8 G-HILZ
RV8tors

 

[apkp777]

I built a -9. I did so purely on economy and no desire for inverted attitudes. I don't care what people tell you, an o-320 is more fuel efficient than an o-360, ignore anyone who talks about "throttling back", it's hogwosh.

Here are some FACTS about a -9,
1. Cheaper to build than a -7.
2. Great performance, but not as good as a -7
3. Slightly better stability in roll, the same in pitch than a -7
4. Better fuel economy (don't put a 360 in a -9, build a -7 if you must do that)
5. Just as easy to fly as any other RV. Easy to land, but also easy to botch if your not careful.

Ask yourself these questions:

1. Do I want to go inverted? Yes, No or Maybe? A yes or maybe= -7
2. Will I be satisfied with 150KTAS cruise? Yes, No or Maybe? A yes or maybe= -7 or -9. A "no" = -7
3. Can I afford the extra build cost for the -7 (yes, a -7 will cost more)? Yes or No? A no = -9, yes=-7 or -9

 

[Jamie]

1. Cheaper to build than a -7.

How is that exactly? Given the same equipment they are almost exactly the same price. Actually the -9 kit is currently $500.00 more than the -7.

 

[apkp777]

How is that exactly? Given the same equipment they are almost exactly the same price. Actually the -9 kit is currently $500.00 more than the -7.

Jamie, I suppose if you put a o-320 in a -7 you could build them for about the same, however no one does that. It's my guess that if you averaged the build costs for -9's and -7's the average -7 is $5k to $10k more.

Most people building a -7 do so for the extra performance. So adding an 360, perhaps C/S prop, injecting it, add 5 point harness, any inverted systems all would be typical added expenses. Of course you could add all that to a -9 as well, and a cessna 152, but defeats the original intent.

I don't thinks it's a fair comparison, a low performance -7 and a high performance -9.

 

[prkaye]

I'm guessing the O-360 is significantly more expensive than the O-320?
I got my overhauled O-320 with new ECI cylinders from Aerosport Power a couple of years ago for under20k, all-said.

 

[N941WR]

I'm guessing the O-360 is significantly more expensive than the O-320?
I got my overhauled O-320 with new ECI cylinders from Aerosport Power a couple of years ago for under20k, all-said.

Let's see...

My ECi O-360 kit cost $14,934.00 plus shipping. Add in another ~$1,000 for all the supplies and the steak dinner it cost me to bribe an A&P friend help put it together. I'm still under your $20K.

When my -9 first flew with the O-290-D2, I had less than $7K in everything FwF, including the prop.

 

[apkp777]

From the Van's cost estimator:

Sweet Setup
RV-7 Standard kit $20620 $20620
New Lycoming IO-360-A1B6 200HP $36300 $39320
Hartzell constant-speed prop $6720 $11135
Prop governor and cabling $1350 $1350
Firewall forward accessories $3400 $4800
Electronic flight instruments $3200 $4400
VFR cross country instruments $1100 $1100
Nav and landing lights / strobes $890 $890
VFR cross country avionics $2800 $5000
Basic electrical system $400 $1000
Cushions / harnesses $900 $900
Professional paint $6000 $6000
Mid-US standard kit shipping / crating $850 $1000
Tool kit / power tools $2000 $2000
Total Kit $86530 $99515

Lame set up
RV-7 Standard kit $20620 $20620
New Lycoming IO-360-M1B 180HP $26500 $34950
Sensenich metal prop $2940 $2940
Firewall forward accessories $3400 $4800
Electronic flight instruments $3200 $4400
VFR cross country instruments $1100 $1100
Nav and landing lights / strobes $890 $890
VFR cross country avionics $2800 $5000
Basic electrical system $400 $1000
Cushions / harnesses $900 $900
Professional paint $6000 $6000
Mid-US standard kit shipping / crating $850 $1000
Tool kit / power tools $2000 $2000
Total Kit $71600 $85600

Fixed Pitch
RV-9 Standard kit $21120 $21120
New Lycoming O-320-D1A 160HP $24100 $27470
Sensenich metal prop $2900 $2900
Firewall forward accessories $3400 $4800
Electronic flight instruments $3200 $4400
VFR cross country instruments $1100 $1100
Nav and landing lights / strobes $890 $890
VFR cross country avionics $2800 $5000
Basic electrical system $400 $1000
Cushions / harnesses $900 $900
Professional paint $6000 $6000
Mid-US standard kit shipping / crating $850 $1000
Tool kit / power tools $2000 $2000
Total Kit $69660 $78580

Constant Speed
RV-9 Standard kit $21120 $21120
New Lycoming O-320-D1A 160HP $24100 $27470
Hartzell constant-speed prop $6720 $11135
Prop governor and cabling $1350 $1350
Firewall forward accessories $3400 $4800
Electronic flight instruments $3200 $4400
VFR cross country instruments $1100 $1100
Nav and landing lights / strobes $890 $890
VFR cross country avionics $2800 $5000
Basic electrical system $400 $1000
Cushions / harnesses $900 $900
Professional paint $6000 $6000
Mid-US standard kit shipping / crating $850 $1000
Tool kit / power tools $2000 $2000
Total Kit $74830 $88165

 

[apkp777]

I'm guessing the O-360 is significantly more expensive than the O-320?
I got my overhauled O-320 with new ECI cylinders from Aerosport Power a couple of years ago for under20k, all-said.

Not too much difference in the o-320 and o-360, the real jump in o-320 to IO360.

 

[Epepperman]

The 9's sell for less in the secondary market, the 8's get the most
(excluding the 10)

Don't blame me it's the market.

 

[MauiLvrs]

Define Perormance

2. Great performance, but not as good as a -7

That would depend on how you define performance...
If by performance you mean speed that is true. But there is more to performance that just speed. Take the following performance characteristics into account and it is not co clear that the -7 wins performance....
Speed -> -7
MPG -> -9
Take-off distance -> -9
Landing distance -> -9
Stall speed -> -9
Maneuvering speed -> -7
Crash surviveability -> -9 (see stall speed and gliding distance)
Glide distance -> -9
G's -> -7
Aerobatics -> -7
Stability -> -9

When I'm wishin' I had the extra 10-20 in a -7 .... I remind myself how much less I put in at the pump and how much less runway I need.....

If Van was to design the perfect airplane, it would be the RV-16. The best of the -7 and -9 and none of the down sides of either. If possible, I'm sure that he would have. But, as he can't .... we have to choose what is most important...

 

[Ramendala]

Cost difference????

I don't get why a -7 cost more WITH a 360. Maybe -9 drivers don't put in the same avionics but all else being equal a -7 is CHEAPER with the bigger engine

Kit cost for the -7 is -$500 cheaper than the -9 (stated earlier)
Engine (Aerosport New Engine with Lyc's Roller) is $200 more for the 360 vs 320 (equally equipped).

Doing this advanced math tells me that the 7 is $300 cheaper...again apples to apples assuming you are putting in the same options/avionics.

Ryan

 

[David-aviator]

I do not buy into having to spend as much as is quoted here for 7 or a 9.

For example, engine instruments -

EIS-4000P $995 (not $3200-$4300)

Package for Lycoming/Continental 4-cylinder engines includes EIS Model 4000 Instrument, 4 EGT probes, 4 CHT bayonet-type CHT probes with adapters, Oil Temperature Sensor, Oil Pressure Sensor, and pre-wired cables. Save $145.

Same cost saving argument can be made in other areas of the airplane. Its easy to go nuts spending money on all the gee-whiz stuff available, but any RV flies just fine with minimal stuff.

I'd much rather fly a bare bones RV than no RV because all the bells and whistles price it out of sight. They even fly well without paint.

 

[Jamie]

MPG -> -9

According to Van's specs, the -7 is a full 11mph faster than the -9 on the same power. So which airframe is more efficient? The general rule of thumb is you can't increase the critical aoa of a wing without increasing it's induced drag. The -9 stalls slower than the -7, therefore it stands to reason that the -7 wing is more efficient (in terms of drag) than the -9. More efficiency in this case means better fuel efficiency.

Take-off distance -> -9

Nope. According to Van's specs the -7 and -9 have the same take-off distance for the same power and weight.

 

[db1yg]

Vans data:

RV9a/160 top speed solo 195 mph
RV7a/160 top speed solo 200 mph
Difference 5 mph

RV9a/160 75% solo 187 mph
RV7a/160 75% solo 190 mph
Difference 3 mph

Same two airplanes take off performance = Both were 300 ft

However, the 7a's performance was tested with a cs prop while the 9a had a fp.

The relative efficiency comparison between the low aspect ratio wing of the 7a vs the modified ronz on the 9a----well I know the answer to that!

Cheers,

db

 

[Greg Arehart]

I'm not sure what the cost differential is these days (bought my engine in 2007), but at that time there was about $300 difference between the IO320 and IO360. Weight penalty was about 10 pounds. Those two factors combined with high-altitude experience made me choose the IO360. Everything I read indicated that one could achieve very similar performance in terms of MPG with the 360 throttled back slightly compared to the 320. Cruising at 13-17k, I can easily get 25 mpg and often am around 30 mpg (burning 6-6.5 gph at 165-175 mph).

Just my data points. There's nothing wrong with either engine in either airplane.

greg

 

[Jamie]

Yep, I got the numbers mixed up. My mistake.

The relative efficiency comparison between the low aspect ratio wing of the 7a vs the modified ronz on the 9a----well I know the answer to that!

Could you enlighten us? Are you implying that the Roncz is more efficient? If so, then why does Van's testing indicate that it's slower w/ the same power? I'm certainly not an aeronautical engineer -- just trying to learn here.

 

[L.Adamson]

Everything I read indicated that one could achieve very similar performance in terms of MPG with the 360 throttled back slightly compared to the 320.

It's been proved with my 0360 numerous times. A friend fly's his 9A slow (compared to me) and efficent. If he fly's my 6A the same way........the numbers are very close. In fact, one time, he beat his own plane for mpg.
Personally, I'm just not that "efficient". My 6A climbs faster, and out runs the 9A. The 9A has an 0320 & C/S

L.Adamson --- RV6A 0360 Hartzell C/S

 

[N941WR]

...Could you enlighten us? Are you implying that the Roncz is more efficient? If so, then why does Van's testing indicate that it's slower w/ the same power? I'm certainly not an aeronautical engineer -- just trying to learn here.

Here is my take on the wing thing. I am not an Aero type enganiir, so take this with a block of salt!

The -9's wing is longer, so...
1. It has to punch a large hole in the air. Large hole = more drag
2. It produces more lift. More lift = more drag

The fact that basically the same airplane, one with a long Roncz wing and another with a short 23000 series airfoil, and the longer wing version is only 3 mph slower on the top end and 10 on the bottom end, indicates a more efficient wing (and flap).

Look at the ceilings of the 160 hp -7 and compare it to the 160 hp -9. This points to a more efficient airfoil for the -9.

RV-9 w/ 160 HP
Solo ROC: 2,000 FPM, Ceiling: 24,500 Ft
Gross ROC: 1,400 FPM, Ceiling 19,000 Ft

RV-7 w/ 160 HP
Solo ROC: 1,900 FPM, Ceiling: 21,000 Ft
Gross ROC: 1,400 FPM, Ceiling 18,500 Ft

(All numbers are from Van?s website.)

 

[java]

Sigh...

All this talk between the 7(6) and 9 builder/owners quoting numerical and airfoil specifics to be able to claim "theirs is better" is starting to miss out on the questions raised by the OP between these two, very similar aircraft. Seriously... how many airstrips are 9's landing at and thumbing their noses at 7 drivers because it's too short for them to land, and how many 7's are arriving at hamburger runs an hour before the "slow" 9's can get there?

Getting back to the point...

Yes, the 7 will be a little bit "hotter" (relatively... the 7 isn't "hot" in approach as far as im concerned) than the 9, but many relatively low time pilots have been able to safely fly the 7, so as long as you are dedicated and learn the aircraft, it shouldn't be an issue (as with the 9). Both handle well at slow speeds.

Yes, the 7 can be a bit faster due to the shorter wing. The math is easy to figure out what this means on a cross country. It ain't much.

The big difference with the DA-20 (in terms of flying feel) will be the higher speed, climb rate, roll rate, and sink. All these will apply with either the 7 or 9. All can be adapted to by a well trained pilot, with suitable transition training, who trained in a DA-20. I actually think the DA-20 is a good training ship to lead to either an RV-7 or 9. You will already be used to a stick in a side-by-side. Get transition training and you'll be fine in either.

Personally, I think the only material difference is whether you want to go upside down. The 7's speed and 9's low speed abilities are not huge deciding factors, because the 7 is still good at low speeds and lands short, and the 9 is still very fast. Sure, there are other differences, but they start to become an argument about exactly "how many angels can dance on the head of a pin" and many are subjective, which can only be decided individually.

Disclosure: I have about 25 hrs. in DA-20's, 10 in an RV-7, 40 in an RV-6, and zero in RV-9's. I am low time, with <200 hrs. when I started flying RV's.

 

[db1yg]

Jamie,

It was not just the numbers being "mixed up", but also that nasty "fine print" about the equipment on each plane that was missed.

Reference efficiency; note that two equally powered planes, one with the low aspect ratio wing, one with the modified Roncz, both get off the ground in 300 ft (per Vans). The low aspect ratio uses full available power to do this (constant speed prop) while the modified Roncz is able to accomplish this lifting feat with less than full available power (fixed pitch prop). This should give you some indication of relative airfoil efficiency.


Try googling: Airfoil Efficiency: Low Aspect Ratio vs Roncz if you really want to "study up" on the subject.

Back to the original poster---neither the 7 nor the 9 are particularly difficult to fly. The 7 requires slightly faster approach speeds and is somewhat quicker on the controls--but not by much! If you think you would be interested in aerobatics--build the 7---if it is local and cross country you want -- build the 9---mho.

Cheers,

db

 

[terrykohler]

Missing an Important Point

The roll rate of the 9 is nearly identical to a Cessna150 (an 8, for example, will roll nearly twice as fast). Important why? It makes for a very stable instrument platform. Can you fly instruments in a 6 or 7? You bet, but many pilots will tell you they won't do it without an autopilot. With sufficient skills, you could fly an ILS in a Pitts, it would just be a heck of a lot easier in a 9, and probably more precise.
Terry, CFI
RV9A N323TP

 

[simpkinsona]

So which airframe is more efficient? The general rule of thumb is you can't increase the critical aoa of a wing without increasing it's induced drag. The -9 stalls slower than the -7, therefore it stands to reason that the -7 wing is more efficient (in terms of drag) than the -9. .

Using this logic, a high performance glider has a slower stall speed, therefore it has a less efficient wing. You are confusing stall speed with AOA. They are two different things. The stall speed is mostly determined by the wing loading. The 9 has a lower wing loading therefore a slower stall speed. It also has a more efficient airfoil by the way.

None of this is to denegrate the 7. It's a great airplane but so is the 9. Just 2 slightly different missions.

-Andy

 

[SteinAir]

One real easy way to get a straight and objective answer is to do the following:

1) Find someone that has both sitting in the barn (Vans, us, etc..).
2) Find pilots that have hundreds of hours in many different RV's with FP, CS, bog engine/small engine, AND have access to said airplanes at their disposal.
3) Do a poll amongst many of those pilots and see what their overall "1st choice" is when they go fly the majority of the time as to what they lean towards. Next time you call vans or us, just ask the guy on the phone which they choose most of the time.

Cheers,
Stein

PS...I'm fairly certain the -9 rolls much better than a C-150 (even an aerobat)!

 

[terrykohler]

The Bias Will Probably Be Toward What You Built

One real easy way to get a straight and objective answer is to do the following:

1) Find someone that has both sitting in the barn (Vans, us, etc..).
2) Find pilots that have hundreds of hours in many different RV's with FP, CS, bog engine/small engine, AND have access to said airplanes at their disposal.
3) Do a poll amongst many of those pilots and see what their overall "1st choice" is when they go fly the majority of the time as to what they lean towards. Next time you call vans or us, just ask the guy on the phone which they choose most of the time.

Cheers,
Stein

PS...I'm fairly certain the -9 rolls much better than a C-150 (even an aerobat)!

Tough to get an objective opinion on this issue, as most of us are coming in with opinions slanted toward the choices we've made for ourselves. As far as comparisons between an RV9A and a Cessna 150 (as well as a number of other aircraft), I'm relying on data provided by the CAFE Foundation...
www.cafefoundation.org. (research/APR)
Terry

 

[N941WR]

...PS...I'm fairly certain the -9 rolls much better than a C-150 (even an aerobat)!

I have to agree with you Stein.

Although the CAFE report reports the RV-9A's Va roll rate as 53 Rt / 61 Lt at Va and 40 Rt / 42 Lt at Vso compared to 47 & 34 for the C-152, it sure feels like the -9 rolls significantly faster than a 152.

(I find it curious that they do not list degrees per second for rolls to the right and left on the C152.)