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  #41  
Old 02-04-2019, 11:26 AM
rv7charlie rv7charlie is offline
 
Join Date: May 2006
Location: Pocahontas MS
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I suspect that you're getting way too wrapped up in that one '20g' word in the report. The seat back was torn loose at the top, and the instrument panel was caved in. Unless the autopsy said he died of spinal compression, I think you're looking in the wrong place for cause.

Beyond that, do you know how 'vertical' and 'horizontal' are defined in the report? Meaning, are they defined relative to the plane itself, or the earth. The 20Gs could be vertical to the earth, and a 45* angle relative to the plane (nose down, moving both down and forward), meaning a total of *much* more than 6-8 Gs forward on the pilot himself.
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  #42  
Old 02-04-2019, 12:40 PM
TXFlyGuy TXFlyGuy is offline
 
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Location: Jazz Town, USA, TX
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Quote:
Originally Posted by rv7charlie View Post
I suspect that you're getting way too wrapped up in that one '20g' word in the report. The seat back was torn loose at the top, and the instrument panel was caved in. Unless the autopsy said he died of spinal compression, I think you're looking in the wrong place for cause.

Beyond that, do you know how 'vertical' and 'horizontal' are defined in the report? Meaning, are they defined relative to the plane itself, or the earth. The 20Gs could be vertical to the earth, and a 45* angle relative to the plane (nose down, moving both down and forward), meaning a total of *much* more than 6-8 Gs forward on the pilot himself.
Good points. You're questions concerning how the loads were defined makes sense.
My suspicion is along those lines, in that the horizontal forces with vectoring factored in were far beyond the 7.3 G's listed by the CAA.

The report stated he died from head trauma, due to the impact of the glare shield. At 80, he may have been dead already, from the massive vertical G load. There was not one drop of blood that I could see anywhere, on the panel, or the glare shield.
In a similar Kitfox accident, where the pilot impacted everything, there was blood everywhere. Yes, you could see it on the almost black instrument panel. Head wounds are notorious for profuse bleeding, even minor ones. Dead men don't bleed.

Here is what I just received via email from the NZ CAA:

One aspect we don’t know in this accident, is whether or not the pilot actually had the shoulder harness tightened when he took off. If he had some slack in the harness when the aircraft struck the ground, the shock loading on the harness could have contributed to overloading the seat back frame.
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Last edited by TXFlyGuy : 02-04-2019 at 08:29 PM.
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  #43  
Old 02-07-2019, 11:36 AM
keitht keitht is offline
 
Join Date: Jun 2016
Location: coupeville wa
Posts: 36
Default Survivable G loads

Some years back I worked on a research program for a pilot ejection system that would potentially be used for a supersonic ejection. The human factors guys provided numbers for ejection forces. The seat had a rocket that produced 10,000 lb of thrust for 5 seconds ( a controlled explosion). The challenge was to be able to control the attitude of the seat to keep it straight during the decelleration. The control system needed to be able to pitch the seat to the required pith up angle and keep it straight with no yaw. The design numbers were 28 G and no more than 5 degrees of yaw. Larger yaw angles would likely result in serious internal organ damage. Working through the numbers brought the realization that small changes in pitch and yaw would have very large delta G numbers attached much the same as a car or airplane accident injury results show. Commercial airplane internal components are designed and certified to withstand 16 G crash loads. Beyond that and the results are what they are - its all serendipity. Some accident victims will survive a described unsurvivable accident and others will be killed or very seriously injured in an otherwise survivable accident - just the luck of the draw. Far better to concentrate ones efforts in not getting into the accident situation in the first place in my view.
KT
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  #44  
Old 02-07-2019, 12:15 PM
TXFlyGuy TXFlyGuy is offline
 
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Quote:
Originally Posted by keitht View Post
Some accident victims will survive a described unsurvivable accident and others will be killed or very seriously injured in an otherwise survivable accident - just the luck of the draw. Far better to concentrate ones efforts in not getting into the accident situation in the first place in my view.
KT
I agree. In the reference case, even a helmet would not have helped. It appears the deceased may have succumbed to other impact injuries which effectively stopped his heart immediately.

Many of us suspect the victim's age played a role, both in being able to survive the event, and in the reaction time when confronted with the initial emergency.

I have the coroner's report. If anyone wants detailed info, please PM me. This is not to be made public, however. I only offer it as education as to what can and will happen in violent G impacts.
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  #45  
Old 02-09-2019, 10:40 AM
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smokyray smokyray is offline
 
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Location: TX32
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Default G Whiz...

Quote:
Originally Posted by TXFlyGuy View Post
How many 20+ G impacts by RV aircraft have been survived by the pilot? Are 20 G crashes very common, and are they normally easily survived by pilot/passengers?
Several years ago an RV4 was returning from Sun N Fun in FL to TX. Descending for a fuel stop in MS, the pilot became disoriented in marginal VFR, performing a inadvertent very low altitude Split-S maneuver and impacting trees and eventually terra firma. Amazingly, He survived. The NTSB report estimated the G force at impact in excess of 30G's. His story of waking up in the RV4 wreckage was sobering. One thing he mentioned was his 5 point harness breaking which later was determined to have functioned to and failed well in excess of design limits.
One of my F16 Bros survived a ground impact during a night low-level NVG training mission, ejecting at 500+Knots after impacting terrain, sustaining a estimated 15G vertical force followed by the 20+G ejection, avoiding high speed flailing injuries post-ejection and performing a night parachute landing fall (PLF) in mountainous terrain.
He was sore, his neck and spine may never be the same, but He walked away.

Both incidents have one thing in common, a gradual or steady G-onset deceleration rate rather than a sudden impact. The old adage about parachuting that "It's not the fall that kills you, it's the sudden stop" holds some truth.
Have a plan..

V/R
Smokey

The U.S. Army UH-60A, Black Hawk, helicopter is the first helicopter designed and built to modem crashworthiness standards. During the design of the Black Hawk, all common injury mechanisms were considered, and significant attempts were made to eliminate foreseeable injury hazards. Most important, the aircraft was designed to withstand an 11.6 m/s (38 ft/s) vertical impact without acceleration injury to the occupants or collapse of structure or high mass items into occupied space.

Last edited by smokyray : 02-09-2019 at 11:30 AM.
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  #46  
Old 02-09-2019, 11:19 AM
TXFlyGuy TXFlyGuy is offline
 
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And it has been pointed out to me that the history of engine failure related takeoff accidents is not pretty.

Many times the aircraft is stalled out at 30-50' AGL, resulting in a very hard impact. And serious injury, or fatality.

As pilots we need to always lower the nose, maintain min flying speed, and fly the plane all the way through the crash.

Human nature being what it is, many pilots try to stretch the glide, thinking they can make it...and they don't.
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  #47  
Old 02-09-2019, 12:50 PM
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smokyray smokyray is offline
 
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Default Turn of events...

Quote:
Originally Posted by TXFlyGuy View Post
And it has been pointed out to me that the history of engine failure related takeoff accidents is not pretty.

Many times the aircraft is stalled out at 30-50' AGL, resulting in a very hard impact. And serious injury, or fatality.

As pilots we need to always lower the nose, maintain min flying speed, and fly the plane all the way through the crash.

Human nature being what it is, many pilots try to stretch the glide, thinking they can make it...and they don't.
Actually, attempting to turn back is the primary killer on T/O engine failures (according to the FAA Safety Magazine) which is causal to the high descent rate, stall/spin etc.
My Dad, a 50+year CFI survived a catastrophic engine failure on takeoff at 200' in a Cessna 140 with a student. He performed basically a controlled crash in a subdivision cul-de-sac with minor injuries to himself and the student. Key word: survived.
The NTSB report called his landing an "unsurvivable scenario" due to terrain and urban surroundings.

In the hospital Dad shared with me, "I had the greatest temptation to try and turn back to the runway, but forced myself to fly straight ahead and make the best controlled crash I could"

V/R
Smokey

As you mentioned: "Fly the airplane as far into the crash as possible...."
Bob Hoover

Last edited by smokyray : 02-09-2019 at 01:04 PM.
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  #48  
Old 02-09-2019, 01:35 PM
dlomheim dlomheim is offline
 
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Location: (2OK2) OK City, OK
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Default RV-6 Head on collision w/a dump truck

I met an NTSB accident investigator some years ago and he told me about an RV-6 accident he worked the report on. It had an engine failure over urban L.A. and the only place for the pilot to put it down was a California DOT parking lot, so he dropped it in there. He barely cleared a hook and ladder fire truck, then bounced a few times before going beak to beak with a parked dump truck. The pilot and co-pilot were thrown forward by the rapid deceleration, and their shoulder harnesses (hooked to the aft longerons) compressed the tail together until it couldn't do that any longer, and then the double row of rivets connecting the cabin to the tail-cone section failed. The tail-cone then slid forward and both occupants lacerated their heads pretty good on the instrument panel, but both survived. No mention of the G loading in the report, but it seems it must have been pretty high; and by limiting the vertical G-load component by flying the a/c to the ground; they no doubt kept from dying from internal injuries such as a detached heart artery, etc.

Doug Lomheim
RV-9A
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