I would like some opinions about crotch straps. I see 5 point belts from Crow and others but no apparent anchor for crotch strap in front. How about back seats, which do have anchor points for the crotch straps? My inclination is to go with 4 point restraints all around as this is not an aerobatic machine.
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Crotch straps
- Thread starter bob888
- Start date
I don't know the geometry of the -10 seats and belts, but I continue to regret not installing the crotch straps when I built my -6. Without the straps, the lap belt rides up if I properly tension the shoulder belts and I don't like the geometry of that. Also, when it is turbulent, a crotch strap would help prevent my head from bouncing off of the canopy top as frequently.
Auburntsts
Well Known Member
The RV-10 front seats have no provision for a crotch strap. As for the rear, I simply opted not to install the lugs and went with 4-point harnesses. I also went with Van's stock straps vs Hooker or Crow, they work just fine and match my interior perfectly.
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I am not flying yet, but have spent some time in a friend's -10 and would agree with Kyle's assessment. The geometry of the lap belt seems to pull the belt back more than down and if the shoulder straps are pulled tight the lap belt tends to ride up to a less desirable (and maybe somewhat dangerous) across the gut position. Wish there was a good solution to a front seat lap belt!
Safety harness
As a racer, let me provide another prospective.
Most racing sanctioning organizations demand a harness with a sub belt. Some sub belts have multiple attach points on the car. There is a potential for the lower body to go forward under the lap belt especially if the lap belt rides high. The lap belt keeps the lower body from going forward/up, and shoulder harnesses keeps the upper body from going forward. The sub belts help keep everything in proper position. If you don't have a sub belt, tighten the lap belt firmly and then tighten the shoulder harness just snug. Don't tighten a shoulder harness to the point where it pulls the lap belt up. The lap belt needs to ride at the pelvic bone to prevent injury at impact.
We used to drive cars on the street without seat belts. Would you do that now?
Bottom line is that harnesses prevent injury. Don't deny that bad things happen. The better your harness system is, the safer you are.
Jim
As a racer, let me provide another prospective.
Most racing sanctioning organizations demand a harness with a sub belt. Some sub belts have multiple attach points on the car. There is a potential for the lower body to go forward under the lap belt especially if the lap belt rides high. The lap belt keeps the lower body from going forward/up, and shoulder harnesses keeps the upper body from going forward. The sub belts help keep everything in proper position. If you don't have a sub belt, tighten the lap belt firmly and then tighten the shoulder harness just snug. Don't tighten a shoulder harness to the point where it pulls the lap belt up. The lap belt needs to ride at the pelvic bone to prevent injury at impact.
We used to drive cars on the street without seat belts. Would you do that now?
Bottom line is that harnesses prevent injury. Don't deny that bad things happen. The better your harness system is, the safer you are.
Jim
Auburntsts
Well Known Member
Well at the end of the day it's all about risk acceptance. For me I assume the risk of submarining without batting an eye and spend my energy trying to reduce the likelihood of ever having to rely on the seatbelts in the first place. YMMV....
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And yet another example of a decision that really can't, and shouldn't, be made via internet consensus. It is your life, and your airplane. Everyone needs to weigh for themselves the costs and benefits of their choices. FWIW, I understand that geometry of the rear seat makes the sub belt more useful/important than in the front. Personally, I make sure my rear seat passengers use the rear sub belt, and I wish I had one in the front too. But that is just me....
Sub belt
So the question remains, has anyone successfully figured a way to put one in the front seats of a -10?
So the question remains, has anyone successfully figured a way to put one in the front seats of a -10?
Yes. I would like this answer too. I have kept the crotch strap lugs in my rear seats because I would like 5 point harnesses back there. As the previous posts demonstrate, you must know a little more about what you're doing to make a 4-point work well. If coming in for an off airport landing, what is the likelyhood of a rear seat passnger doing this correctly. That being said, even if the front seat occupants are "more capable" I'd love to have 5-point harnesses in the front seats also. If anyone has engineered a way to do this, I'd be interested to know about it. If not, I suppose I'll continue with 4s in the front and 5s in the back.
C'mon Guys!
Someone out there has had to add (successfully) a sub belt to the front seats of the -10...speak up, inquiring minds would like to know...
Someone out there has had to add (successfully) a sub belt to the front seats of the -10...speak up, inquiring minds would like to know...
Did It...
We did install submarine belts in the front seat of our 10. I have had the occasion to actually use belts in race cars and owe my life to seat belts from a car accident. As someone mentioned the most important thing is to keep the lap belt on the pelvis. I made a "Y" with a piece of cable and ran it to the seat frame of the seat itself, so it moves with the seat. Then I attached the belt to the loop in the "Y" cable. No pictures handy, sorry... But is has been done, and I am very happy with the results. - Jason
We did install submarine belts in the front seat of our 10. I have had the occasion to actually use belts in race cars and owe my life to seat belts from a car accident. As someone mentioned the most important thing is to keep the lap belt on the pelvis. I made a "Y" with a piece of cable and ran it to the seat frame of the seat itself, so it moves with the seat. Then I attached the belt to the loop in the "Y" cable. No pictures handy, sorry... But is has been done, and I am very happy with the results. - Jason
Crotch strap attachment idea
I used a bolt through the panel, under the seat. It is high enough to accept the removable Crow attachment, but does not interfere with the seat bottom. I'm sure it is not strong enough to meet all the G load requirements for certified aircraft, but I figured the load is in shear and should be much better than not having a crotch strap. The strap wraps around the front of the seat and must be pulled tight to avoid interference with the control stick. If it doesn't work as well as hoped, I can always remove it. I see no other way to install this?? I'd appreciate comments and suggestions. (Not sure about the attached pictures?? I'll see if they made it??)
I used a bolt through the panel, under the seat. It is high enough to accept the removable Crow attachment, but does not interfere with the seat bottom. I'm sure it is not strong enough to meet all the G load requirements for certified aircraft, but I figured the load is in shear and should be much better than not having a crotch strap. The strap wraps around the front of the seat and must be pulled tight to avoid interference with the control stick. If it doesn't work as well as hoped, I can always remove it. I see no other way to install this?? I'd appreciate comments and suggestions. (Not sure about the attached pictures?? I'll see if they made it??)
Bill,
This is what I looked to do as well. Unfortunate I had the seats done already before I figured out that for this to work the front seats need a crotch strap slot like the rear seats.
Hooker sent me the crotch strap so perhaps one day I'll send the front seats back to DJ at Cleaveland tool and have her put in the slots.
Carl
This is what I looked to do as well. Unfortunate I had the seats done already before I figured out that for this to work the front seats need a crotch strap slot like the rear seats.
Hooker sent me the crotch strap so perhaps one day I'll send the front seats back to DJ at Cleaveland tool and have her put in the slots.
Carl
Carl,
My plan is to wrap the crotch strap around the front of the seat rather than have it come through the seat cushion. I'm thinking this will avoid modifying the seat. The only issue might be the angle of the strap, at the seat belt release?? Also, I need to be careful to make sure the strap is tight enough to stay away from the stick.
Bill
My plan is to wrap the crotch strap around the front of the seat rather than have it come through the seat cushion. I'm thinking this will avoid modifying the seat. The only issue might be the angle of the strap, at the seat belt release?? Also, I need to be careful to make sure the strap is tight enough to stay away from the stick.
Bill
Bill,
The stick is not really an issue.
I tried to just wrap it around the front of the seat - way too far forward to do much good.
The real question is to just go through the seat cushion or go through the seat bottom as well. I'm thinking the later will be what I end up with.
Dj did the mod to my rear seat cushions to add the crotch strap belt - they look like they were always made that way so I'm confident she can add the slot to the front seats.
Carl
The stick is not really an issue.
I tried to just wrap it around the front of the seat - way too far forward to do much good.
The real question is to just go through the seat cushion or go through the seat bottom as well. I'm thinking the later will be what I end up with.
Dj did the mod to my rear seat cushions to add the crotch strap belt - they look like they were always made that way so I'm confident she can add the slot to the front seats.
Carl
How much room is there..
.. between the bottom of the seat panel and the stick mechanizms underneath? It would seem to me that two aluminum angles sandwiched around a seatbelt attach lug, riveted underneath the seat pan would work well.
You'd have to have a slot in the seat pan and also a slot in the seat, but it seems like the lug would be pretty strong this way, especially if you further strengthened the seat pan too. I'm just sure if there's enough room under there to do all that and still allow the seat to slide freely, without hitting any of the stick mechanisms.
.. between the bottom of the seat panel and the stick mechanizms underneath? It would seem to me that two aluminum angles sandwiched around a seatbelt attach lug, riveted underneath the seat pan would work well.
You'd have to have a slot in the seat pan and also a slot in the seat, but it seems like the lug would be pretty strong this way, especially if you further strengthened the seat pan too. I'm just sure if there's enough room under there to do all that and still allow the seat to slide freely, without hitting any of the stick mechanisms.
One of my concerns was not modifying the seat structure. This is designed to provide adequate structure in a crash and did not want to change anything there. Perhaps Carl's thoughts about modifying the cushion and support webbing might be a good idea?? I'll have to see how it all goes together and consider possible cushion modifications at that time.
Bill
Bill
A friend and RV-9A builder once told me the bottom strap is still useful on a non-aerobatic plane, because it can potentially keep you from sliding out from underneath the waist and shoulder straps in a serious accident.
I was chatting with Matt from Crow at AirVenture, and he asked how the new 5-points we got for the RV-6 were working out. I said I hadn’t installed the crotch strap yet because I had some engineering to do - and he responded that the 6-point actually has the crotch strap anchored to the same points as the seat belts, but routes under the cushions (thighs). He said it’s a race-car thing, and he’s sending me a pair to try.
Will report back!
Will report back!
N10KE
Well Known Member
If you talk with the pilot of the RV-9A that went down in South Carolina - he will tell you the crotch straps probably saved his and his passenger’s life. Look at the pictures of the wreckage and you may get a sense of how lucky they are to be alive.
Accident Van's RV-9A N94NF, Sunday 30 June 2024
The pilot was executing a forward slip to land. On short final approach to the runway, as the airplane descended below the tree line of a forest that was to his immediate right, he encoun...
asn.flightsafety.org
I can't offer this community much (anything!) from a build or maintenance perspective (1yr NBO), but I DO have 27 years experience in restraint systems and occupant safety. AmSafe Inc. did (and may still) supply the standard belts for some of the kits. This is why my -10 (and a few other -10s out there
) have 4-point rotary buckle restraints with compact inertia reels which meet TSO-C114....wonder where those came from...
In my other life - from a loads perspective, when we performed dynamic testing on our in-house deceleration test sled for Part 23.562 26g seat testing, the loads were nominal, less than 500lbs in nearly every case. Keep in mind that this is with a very strict test regimen where the lap belt portion is tightened down where it's designed to be, across the hip bones. When properly worn, a high percentage of the total load is transmitted into the lapbelt attach points. The load into the shoulder strap depends on restraint geometry, but for Part 23.562 occupant safety certification, loads must be less than 1750lbs for a single strap and 2000lbs total for double shoulder straps.
Pilots get into trouble when they fail to make sure the lapbelt is LOW AND TIGHT first, then tighten the other straps. When the lapbelt is loose, the body slides forward and under the lapbelt - called "submarining". When the belts are loose, the body starts to move forward and accelerate, and when it does hit something, the results are ugly becuase the load pulse is short and peaks with very high G's. A properly tightened belt causes the crash loads to transfer to the seat/aircraft earlier in sequence, spreading the total crash energy across a longer time period, which lowers the loads seen by the human occupant. And no, people may think they're strong, but no-one can stop your body and limbs from impacting the panel and interior - even in a minor crash. When properly adjusted, the crotch strap serves to maintain the low alignment of the lapbelt so that it handles most of the crash loads. The crotch strap itself takes a very small percentage of the load, assuming the lapbelt is adjusted properly. In every case, the purpose of the restraint system is to keep the occupant in the seat and off the interior and concious. Many have survived the initial crash sequence only to perish in the post-crash fire becuase they were incapacitated and could not self-extricate from the aicraft. Apologies for the long post, but there's a lot going on in crash dynamics & occupant safety.
) have 4-point rotary buckle restraints with compact inertia reels which meet TSO-C114....wonder where those came from...In my other life - from a loads perspective, when we performed dynamic testing on our in-house deceleration test sled for Part 23.562 26g seat testing, the loads were nominal, less than 500lbs in nearly every case. Keep in mind that this is with a very strict test regimen where the lap belt portion is tightened down where it's designed to be, across the hip bones. When properly worn, a high percentage of the total load is transmitted into the lapbelt attach points. The load into the shoulder strap depends on restraint geometry, but for Part 23.562 occupant safety certification, loads must be less than 1750lbs for a single strap and 2000lbs total for double shoulder straps.
Pilots get into trouble when they fail to make sure the lapbelt is LOW AND TIGHT first, then tighten the other straps. When the lapbelt is loose, the body slides forward and under the lapbelt - called "submarining". When the belts are loose, the body starts to move forward and accelerate, and when it does hit something, the results are ugly becuase the load pulse is short and peaks with very high G's. A properly tightened belt causes the crash loads to transfer to the seat/aircraft earlier in sequence, spreading the total crash energy across a longer time period, which lowers the loads seen by the human occupant. And no, people may think they're strong, but no-one can stop your body and limbs from impacting the panel and interior - even in a minor crash. When properly adjusted, the crotch strap serves to maintain the low alignment of the lapbelt so that it handles most of the crash loads. The crotch strap itself takes a very small percentage of the load, assuming the lapbelt is adjusted properly. In every case, the purpose of the restraint system is to keep the occupant in the seat and off the interior and concious. Many have survived the initial crash sequence only to perish in the post-crash fire becuase they were incapacitated and could not self-extricate from the aicraft. Apologies for the long post, but there's a lot going on in crash dynamics & occupant safety.
I am a very close friend of the person that owned thed referenced 9A. I found it for him over a decade ago, ferries it to SC, and flew with him a lot.
He thanked me for helping him with a lot of things in that plane, with the most recent being the crotch straps.
Loo at the included picture. The engine is snapped away about 45⁰ to the left. The instrument panel is folded UNDER the fuselage. The crotch straps that we put in was one of about a dozen miracles that saved them.
He is a doctor and was a race car driver in his spare time so he insisted on getting the best harnesses that he could find.
He is alive and well and preparing for some special checkrides with the FAA after all the surgeries on his leg and the rehab. He "only" had some broken bones on one leg and I think the passenger had minor injuries on one ankle. All this after their feet being on the ground after the crash (like Fred Flintstone).
I can speak in more detail about this OFFLINE as I was able to be there to photograph the scene and help find items (with the FAA). I have permission from my friend to discuss this with discretion.
By the way, all the FACEBOOK quarterbacks were WRONG. He is not a wreckless pilot. He practiced a lot and flew the plane well. It was "one of those things that could happen to each of us". And in their case, they survived. I say, due to 12 miracles in a row.
Did I mention that the right wing of the 9A was left up in the top of a tall pine tree?
He thanked me for helping him with a lot of things in that plane, with the most recent being the crotch straps.
Loo at the included picture. The engine is snapped away about 45⁰ to the left. The instrument panel is folded UNDER the fuselage. The crotch straps that we put in was one of about a dozen miracles that saved them.
He is a doctor and was a race car driver in his spare time so he insisted on getting the best harnesses that he could find.
He is alive and well and preparing for some special checkrides with the FAA after all the surgeries on his leg and the rehab. He "only" had some broken bones on one leg and I think the passenger had minor injuries on one ankle. All this after their feet being on the ground after the crash (like Fred Flintstone).
I can speak in more detail about this OFFLINE as I was able to be there to photograph the scene and help find items (with the FAA). I have permission from my friend to discuss this with discretion.
By the way, all the FACEBOOK quarterbacks were WRONG. He is not a wreckless pilot. He practiced a lot and flew the plane well. It was "one of those things that could happen to each of us". And in their case, they survived. I say, due to 12 miracles in a row.
Did I mention that the right wing of the 9A was left up in the top of a tall pine tree?
Forgot to mention.....
I promised him, while he was in the hospital that I would immediately go add crotch straps to my RV6. And I did.
Agree with Jim,
Personal experience with an 11.2g crash.
They helped save me.
Daddyman58
Jerry Fischer
Well Known Member
I wish I'd had more than just a lap belt in the Commanche 260 in 1992. God was with us that day we put her into some clear-cut in west Central Alabama.
Only injury was a spained wrist by right front passenger who braced for impact by reaching for glare shield.
Only injury was a spained wrist by right front passenger who braced for impact by reaching for glare shield.
Looking forward to hearing how this works out.
A four point seat belt system is fine most of the time. But the lack of crotch strap is a liability in moderate or greater turbulent conditions where the airplane is suddenly pitched downward. Your head is likely to hit the canopy above, and it can hit hard without the crotch strap. The other four points hold you laterally and from front to back, but unless these straps are tight, your head remains vulnerable. Get and use the crotch strap. Jim M
I went from original Vans supplied harnesses in my RV6 to Crow 5 points with the crotch strap. The difference the crotch strap makes is fantastic, even just for normal flying it allows you to strap yourself in tightly which I find makes it much more comfortable to fly aerobatics and whilst in turbulence. If the plane is bouncing around for any reason, I much prefer to be firmly attached to it rather than doing my own thing around the cockpit. The benefit in terms of crashworthiness should be beyond obvious.
20 years ago I sold Shroth harnesses for GA aircraft. In the process did a lot of studying about aircraft crash dynamics and 4 point vs 5 or 6 point. How the harness transfers loads into the body is significantly different without a 5th or 6 point harness. Consider that the body is quite fluid. In forward loads, the body slips under the lap belt of a 4 point harness with the lap belt ending
up damaging organs and breaking the lower ribs, often puncturing the lungs. With a 5th point, the crotch straps primary function is to hold the lap belt on the hips while allowing the shoulder straps to be tensioned without pulling the lap belts up. With the lap belts held on the pelvis, it eliminates the submarining of the body under the lap belt and the related injuries.
6 point harnesses can provide dual points for a crotch straps attachment OR, loop back under the legs to the lap belt attachment points. This ends up something like parachute leg straps.
Unfortunately, the RV-6/7/9 don’t offer a good shoulder strap angle, which can result in some spinal compression from downward forces as the shoulder straps take forward loads. AC43.13-2B chapter 9 has a chapter on shoulder belt attachment geometry.
up damaging organs and breaking the lower ribs, often puncturing the lungs. With a 5th point, the crotch straps primary function is to hold the lap belt on the hips while allowing the shoulder straps to be tensioned without pulling the lap belts up. With the lap belts held on the pelvis, it eliminates the submarining of the body under the lap belt and the related injuries.
6 point harnesses can provide dual points for a crotch straps attachment OR, loop back under the legs to the lap belt attachment points. This ends up something like parachute leg straps.
Unfortunately, the RV-6/7/9 don’t offer a good shoulder strap angle, which can result in some spinal compression from downward forces as the shoulder straps take forward loads. AC43.13-2B chapter 9 has a chapter on shoulder belt attachment geometry.
I learnt a good lesson 2 years ago when I loosened my seat belts to reach for something and didn't tighten them up, and subsequently hit some turbulence. I smacked my head so hard I really thought I had broken the canopy. Then, sadly, I lost a friend this year flying a Sling TSI from CA to Las Vegas. He hit his head in turbulence , landed, told he told his wife what happened, and died a week later in the hospital from head injuries. I used my crotch strap so not sure the crotch strap limits vertical movement when you loosen the shoulder straps. But I use all the straps and now keep them tight.
Robert
Robert
