Pmerems

Pmerems

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Just wondering if anyone knows the history behind the change in gear length from the 6A to the 7A/9A.

I compared the tail heights between the 6A and 7A at the Copperstate Fly-In this past weekend. The tail height of the 6A's were approximately 6 feet while the 7A's/9A's were almost 8 feet. That is a rather substantial change.

I know the rudder is a bit taller but the majority of the difference is in the gear leg lengths.

What is the reasoning behind the change?
 
Just a Guess

I'm going out on a limb to hazard a guess: The longer Main Gear is to lessen the chance of touching down on the nose gear first.

Flame suit on.
 
Horsepower means prop length

I didn't ask Van's but I always thought that allowing 20 additional HP meant the need for a longer prop which in turn needs more clearance. I would have been just as happy with shorter legs!
 
One other thought...

The 7A & 9A have a longer fuselage, thus you would need longer gear legs to keep from hitting the tail on landing.

With the -9, you need longer gear legs than the -7 to get the wing to stall in the landing attitude.
 
The reason could lay in the TD's gear change?

May be the reason for the taller Trike gear is the tallier Tail Dragger Gear?

The Trikes are related to the TG's. The TD level attitude (tail up) was looked at I'm sure. Van looked for some parity between the two gear types, height wise.

Changes to the Tail Dragger version has obvious affects. Ostensibly higher angle of attack in the three point attitude allows slower landings. Another advantage is more prop tip to ground clearance. The RV wing is such a low speed loving monster its impossible to fully stall in ground effect with out hitting the tail wheel first, even with the taller gear. A full stall landing means hitting the tail wheel first, with mains still a foot or more off the ground. This makes a somewhat inelegant "drop it in" technique with little or no advantage over flying on a few MPH faster. The down side is less forward visibility.

The affect of taller gear on the trike is somewhat the same as a TD, in that you can be at a higher angle of attack with the tail tie-down ring in the dirt. Of course with the main being set back further on the fuselage it does no need to be as tall. Also you do get more prop tip to dirt clearance. Taller trike gear makes it harder to climb in and out, with a low wing. The reason is it looks better is probably also a reason. The other down side is more flexable longer gear. That may be a disadvantage with the nose gear which some call a poll vault.
 
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Effects of taller gear


Not sure it looks any better, really not sure it would be any more likely to drag the tail. Sure looks like it may be easier to transfer a lot more weight to the front in a given situation though! Throwing it out for comment!!
 
6A look better then 7A

vlittle said:
I have the answer from Gus Fennell at Van's:

"because it looks better"

That's it.
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I do not think the taller tail looks better. I think the 6A looks better with the 5 degrees nose high attutude. Looks more like a tail dragger.
 
rvpilot said:

Not sure it looks any better, really not sure it would be any more likely to drag the tail. Sure looks like it may be easier to transfer a lot more weight to the front in a given situation though! Throwing it out for comment!!
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The tail dragger crowd is always telling us how their planes (with tail on the ground) look 'cool'. So it stands to reason, 'coolness' is the inverse of tail height above ground. Then it follows that a 6A is more 'cool' than a 7A or 9A.
:D
 
Not sure it looks any better, really not sure it would be any more likely to drag the tail. Sure looks like it may be easier to transfer a lot more weight to the front in a given situation though! Throwing it out for comment!!
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I have considered the same thing. Haven't most of the nose-over accidents involved the newer models?
 
Sam Buchanan said:
I have considered the same thing. Haven't most of the nose-over accidents involved the newer models?
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I was under the opposite understanding. From what I can tell, the newest models have the least, if any, tip-over accidents. I thought this was due to the added 1" clearance of the nose gear fork.
 
Wing span?

I always thought that the ground clearance (gear leg length) increase on the RV-7/9 was due to the increase in wingspan (RV-6 is 23ft., RV-7 is 25ft, and RV-9 is 28ft.)

This would minimize risk of wing tip hitting the ground when sideslipping in a crosswind landing.
 
Sam Buchanan said:
I have considered the same thing. Haven't most of the nose-over accidents involved the newer models?
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For those who have followed the tip over accidents, it seems that the majority have been 7A's and 9A's. This might be meaningful, since I believe the most common flying RV as of now is the 6A. There are almost 3 times as many 6/6A's flying as there are 7/7A's and 9/9A's combined per Van's website. I do not know the ratio of A's to TD's, but assuming it is similar among the models (and I think 9 TD's are rare), the evidence seems to indicate many more tip overs with the newer models.

There can be no question that longer main gear are not helping the situation, but what is not known is if it is a contributing factor in a meaningful amount.

As I've written before

http://www.vansairforce.com/community/showthread.php?t=18885

there are other design changes that almost coincide with the switch to the 7's from the 6's.
 
Good point

rvpilot said:

Not sure it looks any better, really not sure it would be any more likely to drag the tail. Sure looks like it may be easier to transfer a lot more weight to the front in a given situation though! Throwing it out for comment!!
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When we were doing the weight and balance on Brian's -4, it was amazing to see the weight on the tail change with only a little change in attitude.

I also like the way the -6A sits better

Pierre
 
I am biased toward

the -7A stance because I own one :) I do think it makes it look like a larger airplane sitting nearly 2 feet taller. The visibility over the nose while taxiing is much better as well, you are looking down at the ground over the cowling instead of up and over the cowling.
 
hecilopter said:
the -7A stance because I own one :) I do think it makes it look like a larger airplane sitting nearly 2 feet taller. The visibility over the nose while taxiing is much better as well, you are looking down at the ground over the cowling instead of up and over the cowling.
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I'm with you Rooster. Discussions of landing stability aside, the RV7A looks superior because the fuselage is parallel to the ground. I think if you asked independent members of the public, most of them would agree. Only RV6A owners will disagree. And that's only because every mother thinks her baby is beautiful regardless of how goddamn ugly it is.:p

As for RV6 taildraggers. Well they may look OK when they're flying but it's when they're on the ground that everyone sees them close up...and on the ground they look like dumpy down-in-the-arse dinky toys. I remember seeing several in magazines in flight and thought they looked just great. And then I saw one parked at a local strip for the first time and I thought it looked like an oversized toy plane. The RV6 is just way too short of length to be an aesthetic taildragger. Sorry, I couldn't help myself. :)
 
Captain Avgas said:
I'm with you Rooster. Discussions of landing stability aside, the RV7A looks superior because the fuselage is parallel to the ground. I think if you asked independent members of the public, most of them would agree. Only RV6A owners will disagree. And that's only because every mother thinks her baby is beautiful regardless of how goddamn ugly it is.:p

As for RV6 taildraggers. Well they may look OK when they're flying but it's when they're on the ground that everyone sees them close up...and on the ground they look like dumpy down-in-the-arse dinky toys. I remember seeing several in magazines in flight and thought they looked just great. And then I saw one parked at a local strip for the first time and I thought it looked like an oversized toy plane. The RV6 is just way too short of length to be an aesthetic taildragger. Sorry, I couldn't help myself. :)
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My 6A is painted kind of like a P-51 with invasion stripes, and it's real "purty" & gets compliments! :D Happily, the tail is a bit lower, 'cause parallel sitting planes wouldn't look like a P-51 at all! :)

As to your second paragraph regarding 6 taildraggers on the ground ; right on 100% :D

That's what I've been saying all along. Look great in the air, but resemble a squatting dog on the ground! :p

L.Adamson
 
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