WWI Replica Safety

[sheppo]

Video - news.com.au

I hope this link works. I would personally wear a lifejacket flying over water but apparently Darwin was out to lunch when this pelican came unstuck.

Chris

[Machinbird]

Looks like a big Delta Sierra. Beyond gliding distance from land without flotation and no visible survival gear.
Cold water is a first class killer. Below 70 degrees F water temperature, without a survival suit, you would live only a few hours. He was probably standing up in the cockpit to minimize his heat loss.
Good for him there was help nearby.
Sid

[Brad]

Originally Posted by j ferguson

Brad,
Do you think there is a foamable material available that has enough compressive strength to help a tube resist buckling? If so, this is a neat idea.

I'm reminded of older English Morgan Automobile frames which were steel tubes or channels around Ash timber.

I'm not positive. I know there is a foam material sprayed into automotive frames by some racers to make it more rigid... That would probably be a good place to start.

It would be interesting to see the difference in buckling loads if someone wanted to test.

[Brad]

There's the SAE paper (authored by Chrysler) showing how effective the foam is

In SAE paper 1999-01-1785 said "8pcf density gave the best strength to weight ratio." That would be best for rocker panels and frame rails.

FoamTech

Chassis stiffening with foam? - RX7Club.com

http://forums.freshalloy.com/showthread.php?p=1392938

Looks like the foam is maybe only a minimal change...

Wood that fit the longeron tightly on the other hand would probably do wonders. Resistance to crushing (maintain the round section) under load would make it MUCH stronger...

Some tests would be interesting.

[John McKenzie]

Hi , FWIW , ..I don't think that polyurethane foam is suitable in this application ; it mainly lacking in the degree of compressive strength available for the job in hand , which is more of a requirement to resist a local kink which preceeds buckeling of the tube in question . ..The normal application is to stabalise the stressed surfaces which contain it , ie double skinned GRP(sic) monocoque stressed skin shells .
For the "cockpit strengthening" application , IF , one wished to use this idea , a better alternative , which would have a proven abilaty to withstand the loads associated with preventing a tube from buckeling would be , (USA),one of the tube bending filler products on offer from Cerro Metal Products Corp.,....The metal ones may be rather heavy and expensive, but the resin type would be a consideration on economical grounds alone .
There are of course all manner of practical difficulties of application and problems should repairs ever be necessary. This would need a LOT of consideration before its use .
A better alternative would be to insert ,as has been mentioned , a well oiled (sic) ,reasonably tight fitting length of ash or hardwood dowel , ie wood with a good resistance to compressive loading across the grain direction .(It could have even been previously soaked in a propriatory hardening resin ,).
However , out of all of this , it would be far simpler , in terms of any posible future repairs etc. .to use a short length insert of steel tubing ( realy only practical if useing metric size tube ) or to USE A THICKER GAUGE TUBE for this member in the first place . (Alt,is an OVERSIZE on dia,...Your choice! )
Ref Fokker cockpit tubes and the "corner" tube segments ; These could be replaced with a continuous length, (or at least for the pieces that lay along and adjacent to the top longerons ),making this section effectively of double tubeing , and , in order that the longeron is not affected unduely by welding heat ; these reinforcing tubes could be attached to the longerons via some other way , ie clips/plates and s/solder joints.Etc etc.or the cockpit reinforcing tube could be welded to a number of short external sleeves (fitting over the longeron ) , and these , after clean up ,sweat/soldered to the longeron...Again , thought has to be given to the various posible difficulties/ requirements concerning repairs that may be encountered later etc..However , the structure must still be of reasonably ballenced strength , otherwise there may arrise from this alteration , a problem elsewhere. .Regards John M

[John McKenzie]

Hey !!! I don't know how Brad's Post #284 came up as being 55 minutes before my 285 , because it wasn't there when I started to write mine only a few minutes ago ?????? Oh well..The wonders of the computer age ..JM

[Joe Perkel]

As unpleasant as some may find the subject of aircraft accidents, there is still much to be learned by individual analysis of the circumstances, What do I think went wrong?, What would I have done / not done?, What can I learn from this? Should I ever find myself on the "wrong end of the stick", I would like to have it analyzed with this in mind.

Here are some fairly recent WWI replica accidents that are applicable to our little sector. Bad few years for the SE5?, or can the decision chain of events be clearly identified in the last two listed?


Recent SE5, fatal, cause not yet determined.

WPR10LA010



2007 SE5, nonfatal, engine failure on takeoff, (much discussed on this thread, this one a maintenance issue?)

http://ntsb.gov/ntsb/GenPDF.asp?id=NYC07LA232&rpt=fa



2008 SE5, nonfatal, builder / manufacturer error.

http://ntsb.gov/ntsb/GenPDF.asp?id=CHI08CA168&rpt=fa

[drrivah]

Joe-
The 2008 accident report is a lesson all builders should study.

Looks like a General Motors LS1 engine was installed with a -12 degree thrust angle on an SE5A replica. Original specs called for zero thrust angle. 2000ft AGL on the second test flight was an inopportune time to discover the effects of this discrepancy.

First test flight indicated upward pitch despite forward stick deflection. In response, the horizontal stabilizer was adjusted before the second test flight. The resulting deterioration of performance in air (on left turn, loss of ~ 10 mph airspeed at full power, uncontrolled descent of 100 fpm, and eventual right wing drop/stall) indicated an airframe issue, not an engine issue. Also illustrates the design concept of "outside the performance envelope".

Curious whether original SE5A naturally stalls with right or left wing drop, or straight ahead, and if that has to do with the direction of prop rotation. For auto engine installations where rotation is opposite original, is it possible to predict which wing the replica will drop on a stall?

This precautionary tale should be required on the test pilot/builder checklist
discussed elsewhere on the forum.

-pete

[Joe Perkel]

Originally Posted by drrivah

Joe-
The 2008 accident report is a lesson all builders should study.

-pete

Pete,

Hence the reason why I picked this particular one. If the report is accurate, I find it nearly incredulous to believe that a builder (manufacturer) can find himself "unaware" of line of thrust issues regarding his build until after an accident. Before the tailplane (or anything) is adjusted, several key questions need to be asked....

-Why do I need to do this?
-What else can cause this particular problem?
-Is this the correct fix?
-What evidence is in support of the above?

Then independent / unbiased confirmation of everything, should then be the order of the day.

[RobW]

There is more going on here than is in the report... if it were simply a line of thrust relative to tailplane incidence problem... he probably would not have gotten off the ground... as it was though, he managed to climb to 2000'... then run into problems.

From my own experience, when it comes to light plane accidents, the FAA inspector will look for something obvious, jump on that, and move on to the next accident.

I would not doubt that a -12 degree thrust angle would have a significant impact upon performance... but, somehow, he managed to lift off, climb to 2000', then (it appears) mush his way back down to the ground. Therefore, I would think that the problem is much more complex than is addressed in the accident report.

We can all sit here and do a lot of second guessing and supposing... but unless we can get Mr. Krueger to jump in and add to the discussion, I don't think we'll get anywhere.

Rob