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War Stories

Cobra (AH-1G) Accidents/Aerodynamics


Keep the discussion going with your comments!


Bill (Capt C) Chiaramonte - 7Sep2014

Re: Clements &  Brown Cobra accident.  To the best of my recollection, they were covering a scout who took fire and when they went up and started to "roll in" they went into zero-g and got mast bumping that severed the mast.  Whether the lost the tail rotor before or after the mast bumping could not be determined.  It happened not far from Cu Chi south of the main highway.
CPT Bob(?) Malinovsky (?) shortly after the crash also went into zero-g and mast bumping but survived and brought the aircraft back to the corral.  The mast had the shape of a Coke bottle where it had been hammered by the swash plate.  It seemed that a team of Bell Helicopter techs showed up within hours and I believe eventually took the aircraft back to the States.
Moose, help me out on this, I think you were the XO then.

Bruce Powell - 7Sep2014
Great information on the Cobra accident. Thank you. I hope Moose and others can add to it.

The Zero G Maneuver: The First Cobras were more hazardous and complicated than any of us knew. Many of the aerodynamic quirks had to be learned the hard way; with the deaths of pilots. The Zero G maneuver was one of them. We actually use to demo the zero g to students at the Cobra School (Hunter) in late 68. I don't recall if it was part of the curriculm but probably not.

Wikipedia says:
Low-g condition is a phase of aerodynamic flight where the airframe is temporarily unloaded. The pilot—and the airframe—feel temporarily "weightless" because the aircraft is in free-fall or decelerating vertically at the top of a climb. It may also occur during an excessively rapid entry into autorotation. This can have a disastrous effect on the aircraft, particularly in the case of helicopters, some of which need the rotor to constantly be under a non-zero amount of load.

low-g conditions can be disastrous for helicopters. In such a situation their rotors may flap beyond normal limits. The excessive flapping can cause the root of the blades to exceed the limit of their hinges and this condition, known as mast bumping, can cause the separation of the blades from the hub or for the mast to shear, and hence detach the whole system from the aircraft, falling from the sky. This is especially true for helicopters with teetering rotors, such as the two-bladed design seen on Robinson helicopters. This effect was first discovered when many accidents with Bell UH-1 and AH-1 helicopters occurred. These particular helicopters simply crashed without any obvious cause. Later, it was found that these accidents usually happened during low terrain flight after passing a ridge and initiating a dive from the previous climb. Articulated and rigid rotor systems do not lose controlling forces up to 0g, but may encounter this depending on their flapping hinge offset from the mast. However, dangerous situations, as with a teetering rotor, may not occur.

I guess no one really thought about how powerful the tail rotor could be if the main rotor was not functioning (i.e. zero g). The torque of the tail rotor up on that tall tail fin and the pilot pushing the nose forward at the top of his steep climb (making the tail higher) could cause the aircraft to twist and invert in a split second. Not even the SCAS (stability) system could compensate. One of our instructor pilots survived the ordeal, got the severly damaged aircraft on the ground; living to tell the rest of us. I had done this and demoed this many times always thinking that I understood the aerodynamics of it and could control it. I was too dumb, too arrogant, to realize that I was playing russian roulette; and teaching it to others with very few hours in the aircraft. 

Combat Cobra Pilots were dangerous:  
I was told that I was the first combat Cobra pilot to come to Cobra Hall as an instructor (Sep 1968). Instead of the full Instructor Pilot course, they sent me out with an IP for a couple days, then gave me two students. Poor bastards. I hope they made it.

We finally figured out, after killing several students and instructors, that the combat pilots returning from NAM were a real menace. They got away with red line flying in Nam, not unlike the Clements story, then came back and taught the new young skulls of mush to do the same. 

Later on all Combat experienced guys were forced to take the full IP course, and more if needed, before turning them loose on the gullable students.

Pat Eastes - 7Sep2014

I remember being in the front seat with you (Powell) flying and getting some real thrills, although looking back, we were probably taxing your Cobra to close to its limits. In some ways, I wish I would have extended to get Cobra qualified, but past history is just that, and I can feel good in that I was one of the last of the Charlie model guys.

Tom Fleming - 7Sep2014
Good information for all of us who flew the AH-1.  When I went through the Cobra course in 1970 I put the helicopter in to a momentary 0g attitude after pulling out of a dive and lowering the nose abruptly.  Luckily my instructor yanked back on the stick and gave me the lecture about 0g.  I have been mindful ever since.

Moose Marcinkowski - 7Sep2014
I can't comment on the Clements and Brown accident but Bill Malinowsky's mast bumping I can. Bill was on a maintenance test flight putting the bird through the normal events when he got into a zero G situation. He felt it go BUMP...BUMP and began having control issues. So he very carefully brought it back to the corral, landed it and shut it down. We were all amazed that he could bring it back at all. Bill Chiaramonte is right. Bell came out, looked at the bird and put it in a virtual plastic bag to take back to the factory. It was either a case of pure dumb luck or magnificent flying or both. Either way we were all glad he made it back.

Bruce Powell - 8Sep2014
Is there any chance that you or someone in your group could get a hold of Bill E. Malinovsky, and get some photos or comments from him for the website?

Moose Marcinkowski - 9Sep2014
I have lost contact with Bill. When I last saw him it was in the 1st Cav ACCB back in the early 70's. I think Dale has him on the roster but I'm uncertain if there is an address. Some maintenance types will surely remember the incident. It was quite the event.

Bruce Sikkema - 24Sep2014
When I went thru Cobra School in late 69, my instructor taught me to "follow" the aircraft if I got into a zero G condition. When the nose tucked and the aircraft rolled right, we just followed in that direction to get back to a positive G condition  (and for Fred and K.C., if that put you a little over center, that was all right as long as you maintained a positive G).

Bruce Powell - 22Oct2014
Bruce S, In my monthly review of emails I discovered that I had not responded to your input on the Zero G thing. Sorry, I always try to respond to anyone who takes the time to give me input.

I second your comments. That is how we used to teach it.

I was at Cobra Hall as an MOI instructor and branch chief during that period. One of my pilots, Rich Wyder, I think, was really into the aerodynamics part of the Cobra, as was I. I think it was he who cautioned us against doing the Zero G demo (just barely getting into it, then go with the flow as you described). He felt that there could be a situation where even a good instructor pilot could not react fast enough to avoid mast bumping and death (wind, altitude, condition of aircraft, etc). Then it happened. I will try to find more information on the incident, but one of our instructor pilots had it happen and managed a crash landing. Our invincible attitude of being Instructor Pilots was dampened. I'm sure many of the pilots continued the demo with extreme caution, but I am sure that it was not in the syllabus. 

Tom Meeks has put together a draft for our AH-1G section in the History part of the website. I will get it up soon. Here is where your comments and experiences can be logged along with all the Centaur Cobra pilots. When people go to that page we want them to hear from the actual combat pilots of that aircraft and not just the text book information. I will also link your great photos to that page.

Tom worked with me at Cobra Hall (MOI) redesigning the Cobra Instructor Pilot Gunnery Course. He may remember more about this. 

As you think of more things or contact other Centaur Cobra pilots, please clue me in so I can get it all into this section.

Tom Meeks - 22Oct2014
The IP at Cobra Hall that got into mast bumping was CWO Bill Bootle who was in my flight: can't remember who the student was.  His student was into the final phases of training when it happened.  They got into mast bumping when exiting a firing range.  His helicopter was low on fuel, and no ammo when they made a final pass over the range where he did an excelerated climb (unknown alt) and jammed the cycle forward to do a simulated steep gun run.  When he reached the apex, the aircraft started a roll and ultimately crashed.  He did manage to get it upright and at the end, rolled the throttle off and it hit the ground.  That's about the extent of my memory bank on that.

Bruce Powell - 22Oct2014 
Tom, Great memory! So this must have been before you came up to me in MOI. 

I didn't know him personally but I do remember that he was the pilot that formally complained when I was chosen to take the Cobra team to Reforger. He was known as a good pilot but I'm not sure that he had any combat time in the aircraft.

Do you remember any specific actions taken by anyone about the incident? I had it in my head that Wyder predicted it would happen and that we probably shouldn't be doing the maneuver except for teaching the student, or giving him the feeling of, where the "red line" or danger point was. I guess I thought that something more was done or put into action other than "Watch out for that one".

Jack Nemeyer - 22Oct2014 
Bruce, were you there when this crash took place ???? I was and I think Ken Rucki was on the crash investigation team... Just for Information.

Bruce Powell - 23Oct2014
Jack, re: Mark Jackson crash I left in late Aug of 1968. The Mark Jackson crash was 28 Oct 1969. We can try to find Ken Rucki and see if he has anything to add based on his participation with the crash investigation team. Dale Dow may be able to put you intouch with both he and Dooling since they are both shown on his roster as located. 

Jack Nemeyer - 23Oct2014 
I talk to Ken Rucki on a monthly basis.....( forwards mostly)..... I just don't have his address on this computer...  I'll dig it out and send it to you.....

Moose Marcinkowski - 23Oct2014
In May of 1968, when I went through the Cobra transition, my IP warned me about keeping positive G's on the rotor system. Furthermore coming out of a dive we were to apply judicious use of both power and cyclic. If we just used cyclic we would hit the ground in a level attitude. This was different from my fixed wing training where stick was applied to level the aircraft and then power was added The Cobra was new enough at that point that all who flew it, both IP's and students were somewhat cautious and we tried hard not to get into compromising positions. So Bruce's comments about Vietnam Cobra pilots being a menace are close to the mark.

Tom Meeks - 25Oct2014
Bruce, I’m pretty sure it was early in 1970.  He and I were in the same section in MOI.  I remember you telling me he had complained about not going to reforger.  He did have some combat time in the Cobra before he got to Cobra Hall.  I met him at Bein Hoa when I went there for the transition program and gave him his first ride in the Cobra. He was there for the class right after the one I was in.  I knew him from my flight school class.  

I don’t remember anything specific happening after the accident but we did get a lot of info suddenly on “negative G’s” and aerodynamics.  I also remember there was a lot of discussion then on how/what we needed to do to not get into that situation.  Basically what you said, we stopped going to the extreme on demonstrating that maneuver and talked about it more.