VansAirForceForums  
Home > VansAirForceForums

- POSTING RULES
- Donate yearly (please).
- Advertise in here!

- Today's Posts | Insert Pics


Go Back   VAF Forums > Model Specific > RV-7/7A
Register FAQ Members List Calendar Search Today's Posts Mark Forums Read

Reply
 
Thread Tools Search this Thread Display Modes
  #91  
Old 10-06-2010, 12:59 PM
Steve Sampson Steve Sampson is offline
 
Join Date: Aug 2005
Location: N. Yorkshire, England
Posts: 1,050
Default

Quote:
Originally Posted by Raiz View Post
Now here's one to get you thinking. The equivalent anaysis of leg failure rates for the UK Vans fleet shows they are much more likely to suffer nose leg failure than the US fleet:

Model ___________________________ 6A __ 7A __ 8A __ 9A
US # failures per 1000 aircraft-years _ 3.5 __ 5.7 _ 3.3 __ 3.9
UK # failures per 1000 aircraft-years __ 28 __ 44 __ N/A __31

The N/A is because there have been no nose leg failures in the UK on 8As (there are only 2 flying).

The rate of nose leg failures is about 8 times higher (across all models) in the UK than the US. Why? If it were piloting technique, we would expect to see a higher accident rate for the fleet overall but this is not the case. The # accidents per 1000 aircraft-years for all 6, 7, 8 and 9 (TD and nose-gear) combined for all accidents except nose leg failures is 6.6 for the UK and 8.0 for the US.

The only thing that comes to mind is that a much larger proportion of UK RVs are operated from grass strips.

Raiz
Raiz, I had a -9a the second in the UK I think which I operated off grass in N Yorkshire. I sold it because I saw an accident waiting to happen when on soft grass.

The point I wanted to add, after having not seen it in the previous 80 odd posts is that soft grass compounds the problem that your analysis highlights. As the weight of the plane settles on the grass it moves the mains back a little. The result being full up elevator is unable to hold the nose off very long after touch down. Since the mains are now further aft than normal the loading on the nose wheel is further increased which only exacerbates the situation which you have analysed.

I suspect it is not an insignificant increase though.

With its shorter main gear legs the -6a is less susceptible to this.
__________________
Steve

G-IKON Build log here , or Index to blog here.
RV4 #4478 - Flying since 16th June '08. First flight video here.
Circuits at my 1000' strip.
Reply With Quote
  #92  
Old 10-07-2010, 02:31 AM
Raiz Raiz is offline
 
Join Date: Nov 2009
Location: Cambridge, UK
Posts: 68
Default Soft ground

Steve I think you make a very good point. The soft ground not only moves the rears back but it also creates a braking effect on the mains, which also tends to load up the nose gear even more.

Soft ground also plays a role on the nose wheel loads directly, because it increases the rearward component of the load on the nose leg, encouraging it to fold under.

Ray
Reply With Quote
  #93  
Old 10-10-2010, 01:08 AM
Agent Cooper Agent Cooper is offline
 
Join Date: Jan 2010
Location: Kempton Park
Posts: 26
Default

Maybe a stupid question BUT what are the efects after landing and the flaps are quickly removed and the stick in an aft pos, does that not lift the nose weight better than all the way on the rough runway with flaps down.

Thsis a a great concern to me having made my choice on a RV7A and now this reading.

Here in SA some of the strips are very much called a bush strips.
Reply With Quote
  #94  
Old 10-10-2010, 04:17 AM
penguin penguin is offline
 
Join Date: Jan 2005
Location: England
Posts: 1,064
Default

Agent Cooper,

I'm not sure it would make that much difference - once you're on the ground the balance of forces is now about the main wheels, rather than the CofG. Also the ground attitude is at a low angle of attack, so the lift produced will be low, and the speed is dropping. I find that landing on bumpy strips the inertia effects predominate - the aeroplane pitches and I bounce over bumps without the elevator authority to do much about it, especially with an aft cofg. I try to minimize the nose wheel load and lower it to the ground smoothly before I run out of elevator authority.

Pete
Reply With Quote
  #95  
Old 10-10-2010, 04:47 PM
Finley Atherton Finley Atherton is offline
 
Join Date: Nov 2005
Location: AUSTRALIA
Posts: 724
Default

Quote:
Originally Posted by Agent Cooper View Post
Maybe a stupid question BUT what are the efects after landing and the flaps are quickly removed and the stick in an aft pos, does that not lift the nose weight better than all the way on the rough runway with flaps down.

Thsis a a great concern to me having made my choice on a RV7A and now this reading.

Here in SA some of the strips are very much called a bush strips.

I mostly operate out of a short grass strip and always immediately raise the flaps at touchdown. Although I have not done accurate testing, my seat of the pants impression is that raising the flaps allows the nose wheel to to kept off the ground to a slower speed, allows more control when lowering the nose to the ground and helps keep the nose in the air while applying brakes.

Opinions vary but I find average Australian grass and gravel strips OK in my 9A. I would keep away from soft, badly potholed and strips with short/sharp undulations.
Read all the suggestions on correct pilot technique and modifications and incorporate those you think are sensible. One extra modification I did that is rarely discussed is to alter the nose fairing cone to increase the fairing clearance fwd of the tire.

Fin
9A
Reply With Quote
  #96  
Old 10-12-2010, 08:06 AM
Ron Lee's Avatar
Ron Lee Ron Lee is offline
 
Join Date: Jun 2005
Posts: 3,276
Default

I just saw this for the first time today. I have a question about the suspension value for the nose tire.

Does that imply that the tire compresses until the bottom rim almost touches the ground? If so, where does the tire go? In other words, does the tire bulge outward possibly contacting the wheel pant? If so, what does that do to the scenario?

I also saw three psi values: 25, 30, 35. I assume that is the nose tire pressure. Interesting that you seem to get less suspension as the psi goes up. I recently upped my nose tire pressure to 40 psi thinking that was the way to go. True or not on a 6A?

Last edited by Ron Lee : 10-12-2010 at 08:12 AM.
Reply With Quote
  #97  
Old 10-12-2010, 11:42 AM
Pilottonny Pilottonny is offline
 
Join Date: Jan 2006
Location: Belgium
Posts: 645
Default Interesting......

Ron, that is an interesting thought!

I let the air out of my front tire just to check that it would not catch on the fairing, if I would ever encounter a "flat" during flight or landing. But..... what you are saying is something else!..... if the tire is flattened by the load of the gear, it will not just be "flat" but it will bulge out!... a lot! And then.... it will catch on the fairing for sure! (unless you have more than the additional clearance that I already have, I guess)

I will be following this discussion!

Regards, Tonny.
__________________
"Pilottonny"
Tonny Tromp
Lanaken, Belgium (EU)
RV9A, Registration: PH-VAN
ECI-Titan IOX-320 with dual EI, turning a Whirlwind 200RV CS prop.
Sold
Reply With Quote
  #98  
Old 10-12-2010, 12:01 PM
todehnal todehnal is offline
 
Join Date: Jan 2005
Location: Kentucky Lakes area in KY
Posts: 933
Default Another RV Nosewheel

I am curious why the RV-12 has not been considered in this discussion. Is it due to the fact that the nose wheel tire is a 500 X 5" just like the mains, or the fact that it has less weight to support. As far as I know, there have been no RV-12 nose gear failures or roll overs. True though that there are less than 50 flying. Also, many of the ones that are flying don't have wheel pants yet. There is a youtube video showing a landing on a pretty rough island sod strip. Can't see the nose wheel, but you can tell from the cabin oscillations that it ain't the smoothest!!
Hope the below link works.
Tom

http://www.youtube.com/watch?v=nOKvd...e=mfu_in_order
__________________
2013- RV12, Kit #119. N123M First flight Nov21. It's a keeper!
1998- RV-9 tail kit, built and sold
1989- RV-6 tail kit, built and sold
Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT -6. The time now is 08:39 AM.


The VAFForums come to you courtesy Delta Romeo, LLC. By viewing and participating in them you agree to build your plane using standardized methods and practices and to fly it safely and in accordance with the laws governing the country you are located in.