Flybuddy2

Flybuddy2

Well Known Member
Question for those who may have flown both aircraft. Given wing loading numbers it would appear that the 7 should provide a better ride in turbulence than the 9. Is this actually the case though or is it a minimal difference? Tom
 
I suspect there is a difference but since I can't fly in two different airplanes at the same time, in the same air, it is hard to tell.
 
It can beat you to death...

....is what I've found in my -6A after a cold front has come through. I've been hit so hard at 190MPH that my back almost hurt so I slowed down. I'd suspect that the -9 wouldn't be much different.

That said, turbulence is a subjective word anyway.....to some, a normal bumpy summer afternoon is rough......to veterans, just another day.

The best,
 
Whichever plane is heavier will give you a smoother ride. I doubt there is any difference between a -7 or a -9
 
The difference probably can not be measured. What really matters, other than weight, is speed. Slowing from 150 to 110 helps a lot to make the ride tolerable. Flying these things in really rough air is a full time job.
 
A copy & paste

Intensity

Light
Turbulence that momentarily causes slight, erratic changes in altitude and/or attitude (pitch. roll, yaw). Report as "Light Turbulence".

OR

Turbulence that causes slight, rapid and somewhat rhythmic bumpiness without appreciable changes in altitude or attitude. Report as "Light Chop".
Occupants may feel a slight strain against seat belts or shoulder straps. Unsecured objects may be displaced slightly. Food service may be conducted and little or no difficulty is encountered in walking.

Moderate
Turbulence that is similar to Light Turbulence but of greater intensity. Changes in altitude and/or attitude occur but the aircraft remains in positive control at all times. it usually causes variations in indicated airspeed. Report as "Moderate Turbulence".

OR

Turbulence that is similar to Light Chop but of greater intensity. It causes rapid bumps or jolts without appreciable changes in aircraft altitude or attitude. Report as "Moderate Chop".
Occupants feel definite strains against seat belts or shoulder straps. Unsecured objects are dislodged. Food service and walking are difficult.

Severe
Turbulence that causes large, abrupt changes in altitude and/or attitude. It usually causes large variations in indicated airspeed. Aircraft may be momentarily out of control. Report as "Severe Turbulence".
Occupants are forced violently against seat belts or shoulder straps. Unsecured objects are tossed about. Food service and walking impossible
 
Maneuvering speeds

There is a chart in my RV-7/7A builders manual that lists Va for the different models. If my memory is correct, Va for the 7 and 8 is 142, and for the 9 it is 118 (don't remember if it is in MPH or knots). That was one of the factors i used for choosing the 7 over the 9 (but that is a different thread :)).
 
I have much more time in 6's & 9's than a 7. But between the 6 & 9 (my 6 has a higher wing loading).............the difference is too minimal to tell. A friend with his 9A often flies on cross country flights with our 6A. If the air is choppy, we both get bounced around ------- much the same.

L.Adamson --- RV6A
 
At the same speed, the -7 should give you a better ride with the higher wing loading. However, one doesn't build a -7 to travel at -9 speeds, right? :)

TODR
 
the_other_dougreeves said:
At the same speed, the -7 should give you a better ride with the higher wing loading. However, one doesn't build a -7 to travel at -9 speeds, right? :)
Click to expand...

The friend of mine really likes to fly at fuel conservative speeds in his 9. So when I fly along, I'll sometimes pull back to these these "tortoise" air speeds too. And even though my 6A has a higher wing loading, it just doesn't make a noticeable difference in turbulence. So we can throw the theories out, based on actual experience. :D

L.Adamson --- RV6A
 
L.Adamson said:
The friend of mine really likes to fly at fuel conservative speeds in his 9. So when I fly along, I'll sometimes pull back to these these "tortoise" air speeds too. And even though my 6A has a higher wing loading, it just doesn't make a noticeable difference in turbulence. So we can throw the theories out, based on actual experience. :D

L.Adamson --- RV6A
Click to expand...
I notice a HUGE difference in the CT when I go from light (9 lb/sf) to heavy (13 lb/sf) after picking up fuel and a passenger in the same stop. However, unlike the -7 vs -9 comparison, that's not changing the span or airfoil, just the loading and CG.

TODR
 
Wing loading according to Van's numbers

RV-6: 14 RV-6A: 15
RV-7/A: 14.8
RV-8/A: 15.5
RV-9: 12.9 (118 hp), 14.1 (160 hp)
RV-10: 18.6

The 160 hp RV9 wing loading is not that much different than other two seat RVs. Rough air handling should not be a major factor in selecting RV models.
 
Personally I think there is a big difference between the 7 and 9 in rough air. I have logged about 150 hours in a 9A and about 7 hours in a 7A and I think there is a significant difference in the ride especially when there is a bit of turbulence. The 9 seems to be much more sensitive to turbulence than the 7 and I have bumped my head on the top of the canopy in both airplanes. I have never flown a 7 solo so that probably has a bit to do with my perception however I?m still convinced the 7 provides a much smoother ride in bumpy or turbulent conditions that the 9. I don?t understand why because the wing area of the two are almost identical, within 3 sq feet and the weight not too much different however the additional 6 gallons of fuel in a 7, slightly heavier engine and the fact that I have never been solo in a 7 may be the explanation or perhaps it has something to do with the extra 3 foot wingspan of the 9. One particular experience stands out; I flew solo to an airport in the 9A at about 1000 ft AGL and was getting bounced around pretty good, 120 MPH was as fast as I wanted to go. I landed and got into a 7A with a friend, took off and flew at the same altitude at 170 MPH and the ride wasn?t bad at all, a bit bumpy but no fear of banging our heads on the canopy. I would be surprised if the additional weight we had in the 7 could explain the much smoother ride especially at 50 MPH faster than the 9.
 
It's not the weight of the aircraft that make the ride smoother...it's a function of both Wing Loading and Aspect Ratio. I believe the aspect ratio in the 9 is slightly higher than the 6 or 7 (not 100% sure, though). Longer, skinny wings are more subject to turbulence than short stubby wings, even if they're at the same Wing Loading.
 
All things being equal, if you add a passenger to an airplane the weight of the aircraft goes up and so does the wing loading and manuvering speed, the ride also becomes smoother. Yes, the aspect ratio of the 9 is significantly higher than the 7, about 6.32 compared to 5.16.
 
handling vs speed

tc1234c said:
(snip) The 160 hp RV9 wing loading is not that much different than other two seat RVs. Rough air handling should not be a major factor in selecting RV models.
Click to expand...

Rough air handling may not be a factor, but rough air speed difference (Va) between the -7 and the -9 (24 mph) could be a factor for some.
 
Hmmm, Va is the speed at which full flight control (elevator) deflection will not cause any structural damage prior to the airplane stalling.

We seem to be discussing the maximum structural cruising speed, Vno. This is not Va. Vno is the top of the green arc and is the smooth air operating speed. Flight above this (yellow arc) is supposed to be only in smooth air as vertical (up or down) accelerations due to gusts or turbulence may cause structural damange before the airplane has a chance to stall.

As it concerns a smooth ride, that is a function of inertia. A heavy object will be more resistant to change in motion than a light one. So both airplanes -7 and -9 should have very similar ride characteristics. Since I haven't yet installed an airspeed indicator in my plane yet, I don't even know what the V speeds are for it. I assume the Vno is less on the -9 because of the longer thus weaker wing.

Va is importantant because you get protection from a stall and structural damage in heavy turbulance. However, Va is usually less than Vno and even though the -9 has a lower Va, that does not mean that you have to fly Va in turbulence. You should stay below Vno.
 
Vno

Taken from POHs listed on VAF.

6 : 180 mph
7 : 193 mph
9 : 180 mph

My personal experience (limited flight on 6A and 7A) is that there are small differences among them (<10% on Vno and <10% on wing load). Between 7 and 9 the major difference is aerobatics. 7 also allows larger power plants thus speed. Again, percent speed difference is small when compare them with 172s and Warriors.
 
The decrease in Va is caused in large part by the decrease in stall speed of the 9.
tc1234c said:
7 also allows larger power plants thus speed
Click to expand...
But not much as power increase requirements is exponential. So the 20-40 HP increase in the 7 doesn't buy a lot of speed.

apkp777 said:
As it concerns a smooth ride, that is a function of inertia. A heavy object will be more resistant to change in motion than a light one. So both airplanes -7 and -9 should have very similar ride characteristics.
Click to expand...
Humm, use a little math and physics to answer the question ;)
 
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roughing it

well.........lots of replies, but few concrete comparisons.
I've ridden briefly in a -6a, and it definitely felt solid, landed fast, and seemed to penetrate light turbulence well.
My -9a, on the other hand, is more like a leaf in a hurrricane! I frequently hit the canopy, and throttle back for a smoother ride. Wing loading may be similar, but at the typical weights I fly, seems there is a lot of divergence from straight & level. The longer wing, when upset, creates a bit more roll.
(I might compare it to flying solo in a 152, vs a 172, if we've all flown those!?!)
it's all tradeoffs; I like the leisurely pattern and landing speed of the -9, so that's what I chose. If I have to slow down to soften the bumps, that also fits my mission profile. YMMV.
 
flyboy1963 said:
The longer wing, when upset, creates a bit more roll.
Click to expand...
You do get a lot more of that rolling motion with a long winged / high aspect ratio airplane. I find that quality admirable in sailplanes (e.g., Duo Discus, 20m / 66ft span); good for helping sniff out thermals.

It's not so good in a traveling airplane. Try flying under the mixing layer on a hot Texas afternoon in a DA40 (39ft span) and you'll nearly get seasick with all the rolling and yawing.

TODR
 
The final point...........:D

The friend of mine (RV9A) contacts me on the radio as we're flying cross country a few miles apart. He say's "you getting bounced around like us?"

I say "yes".... :)

L.Adamson --- RV6A

And P.S. ---- this happens every time we're at the same altitude. And we both have passengers for around the same load.
 
flyboy1963 said:
The longer wing, when upset, creates a bit more roll....
Click to expand...
The wings are only a foot and a half longer on each side. not very much. May not be very noticeable. The wing loading is very similar also (RV9A=14.1 lb/sqft RV7A=14.8 lb/sqft). Any difference may be more likely attributed to the higher lift generated by the 9's high lift wing.
 
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Well, I got to spend some time in both the 7A and the 9A. Both were kept in my hangar with the understanding I could fly either one in lieu of hangar rent.:) I would literally get out of one and into the other one when giving rides to people. I never really noticed any differences in any kind of turbulance.
I will tell you that I always seemed to make better landings in the -7A. I don't know why, but that particular 7A seemed to be easier to fly, I also had less time in it over the 9A. The 7A had c/s prop where the 9A is fixed.
All in all, though neither was hard to fly and both are fun.

Marshall Alexander
 
Marshall,

I think the difference was probably the prop. I gave a friend who is a CFeverything some left seat time in -9 prior to the first flight in his -7. Later I asked him which was easier to fly and he replied the -9 was much harder to land. He credited that to the CS Prop in his -7 with the difference.
 
N941WR said:
Marshall,

I think the difference was probably the prop. I gave a friend who is a CFeverything some left seat time in -9 prior to the first flight in his -7. Later I asked him which was easier to fly and he replied the -9 was much harder to land. He credited that to the CS Prop in his -7 with the difference.
Click to expand...

Okay...........back to my 6A & the other 9A which both have C/S props. My 6A is not a 7, but the other end of the spectrum from the 9. Close enough.. :D

My 6A with C/S and the 9A with C/S land much the same. Both will descend and slow down fast. Both will "fall" thru the flare if you let the speed decay too much. The 9A with C/S won't be floating along in ground effect to save your rear.

The 9A lands 10 mph slower than my 6A. My 6A's decent rate with power off is more than the 9A's.

But in the end, the technique and feel is much the same. My 6A uses knots for airspeed, and this partucular 9A uses mph. Therfore, we use the identical approach & over the fence speeds. There is just about a 10 mph difference between kias & mph at approach/landing airspeeds.

L.Adamson --- RV6A
 
my $.02

My -9A definitely yaws more in a direct crosswind than my bud's -6 due to the larger VS and rudder. We both pretty much got the s**t beat out us coming home from LOE on the leg from Aztec, NM to Ogden, UT. IIRC winds aloft were in the neighborhood of 50-60 out of the west.
I compare the ride between the 9 and the other the other RVs to the ride between high wing Cessnas and early Cherokees with the "hershey bar" wing. The Cessna and the -9 ride softer and tend to float more. An earlier post mentioned a leaf in a windstorm. On the other hand, the Cherokees and RV3,4,6,7,8 have a firmer ride that you'll feel in your seat and in your teeth fillings.
 
re: same speeds

Bill, I too accredited the easier handling of the 7 to the c/s prop.
And L. ??? funny you mentioned the kph/mph. The 7A was kph while the 9A was in mph. I would come in over the fence at 75 in either airplane. Made it pretty easy for my simple mind.:D

Marshall Alexander
 
I have some time in a 7, but not enough to really judge the ride. I suspect it is similar, all other things being equal. I will say my 9A seems to yaw more in turbulence. I find a great difference in ride above and below 150 mph tas. If it get pretty rough, I just drop to around 145 tas. It seems more related to tas than ias, so it pays in two ways to be up high. Below 150, the ride is similar to a Cherokee at cruise, above 150 it feels "sharper."

Bob Kelly
 
Higher wing loading is the key

All things being equal, the A/C with the higher wing loading will give you a smoother ride. Those who have flown both A/C will have had to do so under near identical conditions to make a valid comparison. If the two planes are loaded with the same weight, the one with the greater wing loading will better resist a given amount of turbulence (think of a greater force being applied to the wing).

That being said, the best way to reduce the jolts you feel from turbulence is to slow down. Energy is the square of velocity. You could slow a -7 down to the speed of a -9 to get a smoother ride. Personally, I chose different factors for chosing which airplane to build though.


Cheers,

David
 
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