Text Box: WARBIRD NOTES #33        6 Jul 99   (5)   
SPOILERS ("SNAKES") ON THE WINGS
Many years ago I learned something on one of our airline overnights that's stood the test of time for me.  I'd written a letter about this almost five years ago and was reminded of it again this very morning when someone called me about wind damage he'd experienced on his DC-3.  So far, in every case of this I've always been impressed with (1) the person involved feeling a sense of outrage mixed with a feeling of "how did this ever happen to me" and (2) his feelings of "if I'd just have known the wind was coming, I could have done something."  This seems to be a universal feeling, shared by anyone who's had it happen to them.  Well, in this case, they shouldn't be so hard on themselves since they aren't alone.  However, there is a solution. Perhaps not a perfect and all encompassing one, aviation things just aren't, in my experience.  If you want to believe they are, then I've got some "ocean front property in Arizona" - and - just for you, it happens to be for sale!  

In 1994 I'd written the letter quoted below to Bob Thompson, who was at the time Chief of the General Staff of the Confederate Air Force.  I'll just quote the original letter below, then add a few remarks from today's perspective.

 

"In the last letter to the members of the Flight Safety Board I wanted to answer a question from some of them concerning the status of the attempt to minimize the possibility of wind damage to CAF equipment out on tour.  I mentioned this almost in passing at the end of the last letter.  I've just gotten some feedback on this and wanted to touch base with you about it.

 

If you recall, at the Midland FSB meeting we discussed the wind damage the CAF has encountered over the years and this past summer in particular.  After the FSB meeting I had to report our recommendations to you gentlemen on the General Staff.  One of our recommendations was based on our airline's experience with DC-3s remaining outside on the ramps in all kinds of weather.  I specifically remember one night in Battle Creek when the winds had exceeded 75 knots.  No damage occurred and the airplane remained exactly where we had left it.  I remember that was the first time I had seen what were called "snakes", which were nothing more than 3 or 4 inch surplus fire hose filled with fine sand.  These were in short enough lengths that they could be thrown up on the top of the wing by a couple of people.  Once there they conformed to the shape of the airfoil and didn't move.  This simple device destroyed the airflow and prevented the wing from doing what it does best - lift!   

 

Bob, you can tie aircraft down until eternity but you cannot argue with the basic laws of nature.  Let's use the DC-3 for an example.  A wing designed to create 25,000 pounds of lift will generate that lift when the wind exceeds the takeoff speed.  Power on I can get a 3 down in the high 60s before stalling, with no power it's a little faster.  Now remember the airplane is parked in a three-point attitude, an attitude that places the wing in its maximum lift-generating stance.  Any rope/chain/cable tiedowns aren't going to stand a snowball's chance when mother nature creates forces like this.  The only thing that works is to destroy (spoil) the lift.  We've had pilots on the airline that wouldn't use the automatic spoiler feature of the DC-9 simply because they are so effective, creating a "dump" when the guy was tying to get a smooth touchdown.

 

During the GS meeting when I presented the FSB's recommendations I remember that Steve Miller was seated beside me.  When the GS approved it I really didn't know that any further action was required on the part of the FSB to implement it, we only advise.  I really thought we had discussed it to death and had gone over-ad infinitum-all the things I've written down again above.  Now I get a letter from a maintenance officer on the C-46 who describes it as "ludicrous".  I really don't know if he is in full possession of the facts or whether he simply chooses to misread them along with the "reliable aerodynamic engineers" he quotes.  I talked with Billy Thomas and he is only in possession of a skeletal set of recommendations adopted by the GS.  In the letter that maintenance officer says that "sixteen tons" of sand wouldn't have had an effect.  I can't believe that someone thinks that I think the weight of the sand matters like it's going to hold the airplane down with muscle.  I only described what works at a home base or other location where the "snakes" can be kept.  Obviously the same thing can be accomplished for an airplane out on the road with 2 x 4s nailed to 1 x 4s or water filled hose or whatever a motivated sponsor/operator's ingenuity provides.  We've used old tires on the Catalina this summer.  He also mentioned that serious damage could have resulted if the C-46 wing had been cabled.  That is exactly my point!  Tiedowns have no chance against the lift generated by the wings.  This is not to negate, however, the tiedown's function in restraining the tailwheel as described by Billy Thomas.

 

We can never completely eliminate the hazards to these aircraft; we can only do everything in our power, utilizing our combined experiences, to minimize them.  For someone to deliberately fight the efforts to do so raises serious doubts about our goals.  Billy Thomas and Joe Coleman (and perhaps others I am unaware of) performed an exceptional (and largely unrecognized) service to the CAF this past summer in expeditiously returning the C-46 to service.  The tragedy is that it might have been unnecessary!  It sounds as though it was one of those acts of nature that man cannot prepare for.  We don't know and will never know but we should certainly direct our efforts towards preventing a reoccurrence.  This will take all our experiences and efforts in concert, not in bitching about why it can't be done.  We simply cannot absorb the losses we've incurred lately and stay in business.  When I saw the airplanes parked in close proximity as they were at Millville I think that we haven't learned anything.  With the rate of accidents we've had I really don't have time to be composing letters like this explaining what was explained in the past.  Probably in truth this occurrence is not technically a Flight Safety Board problem but we are all in this together, aren't we?"

 

So - that's what I had to say about it back then in 1994!  Certainly nothing that's occurred since then has caused me to change my opinion in the slightest.  One worry that I've recently heard that needs to be addressed is the matter of how much wind it would take to blow the "snakes" off of the wing.  These "snakes" were, to the best of my memory, thrown up on top of the wing from the nacelles out almost to the tips.  I know they remained in that location in some winds that exceeded 80 knots.  They did this because their sand filling wasn't stuffed to a "sausage like" consistency, allowing them to roll off.  They were more "squishy", which let them adhere closely to the top of the wing.  

 

Anyway, here we are, five years later and we're still standing around open mouthed, and figuratively wearing knickers.  By the way, I am impressed - it's just in the opposite direction of what one might hope, I guess!        

 

 

                                                                                             R. Sohn     1999


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