question about manuvering speed in the 9a

[docrick]

I'm about ready to order the empennage and start this crazy thing of building an aircraft.

I am interested in the 9a because of the more docile handling and have no interest whatsoever in aerobatics. This ship will be used for fairly frequent 700 mile or so cross countrys.

With regard to manuvering speed I noticed on Van's site that this speed is 118 mph for the 9a, quite a difference from say the 7a (I'm sure it's the ability for the 7 to pull higher g forces); but 118!

That seems like a big difference from normal cruise speed. I fly from Oregon to Utah and So Cal and at least the trip from west to east there are some bumps along the way.

Now for the question. How bumpy does it have to be to slow the 9a to 118 mph?

 

[kentb]

Remember back to you primary training...

I'm about ready to order the empennage and start this crazy thing of building an aircraft.

I am interested in the 9a because of the more docile handling and have no interest whatsoever in aerobatics. This ship will be used for fairly frequent 700 mile or so cross countrys.

With regard to manuvering speed I noticed on Van's site that this speed is 118 mph for the 9a, quite a difference from say the 7a (I'm sure it's the ability for the 7 to pull higher g forces); but 118!

That seems like a big difference from normal cruise speed. I fly from Oregon to Utah and So Cal and at least the trip from west to east there are some bumps along the way.

Now for the question. How bumpy does it have to be to slow the 9a to 118 mph?

The -9 stall speed is much lower there for VA is much lower. VA is the speed that full deflection will result in a stall of the wing without bending the airplane.

I fly my -9A without reducing speed in conditions that I would slow my Cessna in. The 9A just feels more rugged then the Cessna. Although it tends to fishtail more with turbulence.

Kent

 

[pierre smith]

Welcome

Hi Doc, and welcome.
Bear in mind that Maneuvering speed refers to the max speed at which you can apply full and abrupt control pressures without a structural failure, not the rough air speed. My opinion is that as long as you stay out of the yellow arc in rough air, you'll be okay. There are however, times when a bump so hard makes me hurt my gut or back, that I voluntarily slow my -6 even tho' it's a 6 G machine. At the speeds RV's are capable of, big bangs can happen.

Regards,

 

[docrick]

The -9 stall speed is much lower there for VA is much lower. VA is the speed that full deflection will result in a stall of the wing without bending the airplane.

I fly my -9A without reducing speed in conditions that I would slow my Cessna in. The 9A just feels more rugged then the Cessna. Although it tends to fishtail more with turbulence.

Kent

Thanks. I figured this to be the case, just wanted an experienced RV 9a pilots perspective.

 

[videobobk]

There have been few smooth-as-glass days since I started flying my 9A, and I find it to be quite comfortable in light to moderate stuff. When it gets fairly bumpy, I drop down below 150 mph TAS. Below 150, the bumps are far less "sharp." I don't see this as a problem. I only cruise above that at higher altitudes where usually it isn't so bumpy anyway.

Bob Kelly

 

[Bryan Wood]

One time in almost 500 hours I slowed to 118 mph because of some very bad bumps. We were enroute to Crossville, Tennessee coming in from the west at 7,500' and about 50 miles out when the bumps hit. It was so bad that I couldn't switch the radio over to 122.00 to give a pirep. Every time I tried to turn the frequency knobs a bump would make me either spin it, and/or my hand would get knocked off. Instead I called Center since we were on flight following and reported moderate to severe in case they wanted to warn other airplanes about the horrible turbulance. As I was talking the bumps would make involuntary grunts come out as if getting hit in the stomach and it must have sounded odd to the controllers. A few minutes later after some fumbling I was able to get the number 2 radio on 122.00 and heard them give a warning to all airplanes that an experimental had reported moderate to severe and to be aware. I felt kind of stupid reporting this to center, but after explaining that I had my hands full and that this was the extent of my ability to make a pirep they apparently passed along the information. Now getting to the 118 mph worry of yours. Believe me you will be happy to slow down to this if you actually get into this kind of stuff. When the time comes you will just know! As for the other post above about the tail swimming back and forth in turbulance we have found the same thing with our plane. It's hard to believe with that huge tail but it won't hold it straight in the bumps.

Best,

 

[karl]

TAS

There have been few smooth-as-glass days since I started flying my 9A, and I find it to be quite comfortable in light to moderate stuff. When it gets fairly bumpy, I drop down below 150 mph TAS. Below 150, the bumps are far less "sharp." I don't see this as a problem. I only cruise above that at higher altitudes where usually it isn't so bumpy anyway.

Bob Kelly

Why do you use TAS as your limitation instead of IAS? At 12K ' your IAS could be in the 120's, while at near sea level nearly the same as your TAS of 150, but with a much different ride. Did you mean IAS? No critisism intended, just curious. I know Van is concerned about flying at certain speeds expressed as TAS for fllutter avoidance

 

[videobobk]

Why do you use TAS as your limitation instead of IAS? At 12K ' your IAS could be in the 120's, while at near sea level nearly the same as your TAS of 150, but with a much different ride. Did you mean IAS? No critisism intended, just curious. I know Van is concerned about flying at certain speeds expressed as TAS for fllutter avoidance

Nothing scientific here, but in the couple of times that I have seen any significant turbulence in my 9A at higher altitudes (and therefore relatively lower IAS) the comfort level seemed to me to be more a function of TAS. I haven't been in anything rough enough to really have to cut back as Bryan mentioned. It may just be a perception thing, but that is how it seemed to me. Dropping back a little on speed seems to make more difference in the 9A than in some planes I have flown. Again, not too scientific here, just how it seemed to me.

Bob

 

[Skytrash]

You will not regret building a 9A Doc.

I have over 800 hours on mine and have flown across country twice with many trips between California and Oregon.

There was an article in the RVAtor with a graph that showed how maneuvering speed was determined but the one number that stuck in my mind was a True Airspeed of 157 knots. This was the number where the aircraft structure could take a 300 fpm vertical gust. That is the number I stay below if the turbulence is more than occassional light. If it starts bumping around like Bryan spoke about where you have trouble changing the frequency I would be slowing to below 120 knots TAS.

Most of the time when there is turbulence, there is a good wind blowing and you will also get mountain waves. If you have an autopilot in mountain wave and set it to maintain an altitude you will be reducing throttle to keep from going over the 157 TAS and conversely you will have full power and a dropping airspeed in the down drafts. I have seen the airspeed vary from 160 knots to 90 knots TAS in the span of minutes trying to maintain an altitude. Mother nature is powerful and demands repect.

 

[kentb]

I think that Karl posted above is correct.

For all speeds except VNE, you should be doing things based on IAS. VA is an IAS number. VNE is a TAS number.

Kent

 

[Finley Atherton]

Hi Doc, and welcome.
Bear in mind that Maneuvering speed refers to the max speed at which you can apply full and abrupt control pressures without a structural failure, not the rough air speed.

I have some trouble understanding the practical significance of the manoeuvring speed limitation for the 9. My 9A has so much power in the controls that I find it hard to envisage a situation were you would need to use full and abrupt control deflection even at speeds well below the manoeuvring speed?? Like others have suggested, in turbulence I slow down to a more comfortable speed, typically in the lower half of the green arc.

in 9A

 

[pierre smith]

No

I have some trouble understanding the practical significance of the manoeuvring speed limitation for the 9. My 9A has so much power in the controls that I find it hard to envisage a situation were you would need to use full and abrupt control deflection even at speeds well below the manoeuvring speed?? Like others have suggested, in turbulence I slow down to a more comfortable speed, typically in the lower half of the green arc.

in 9A

Hi Finley,
I'm in no way advocating full and abrupt control usage in any RV. Our American FAA definition of "Maneuvering speed" is what I was quoting only, not using.