Speed Kills (Part 2)

           SPEED KILLS (Part 2)

                      Sixth Edition, Volume 2

 

Well, It’s been a while since I last posted a blog. Life has been very, how should I say, interesting at the very least. So, I finally have some time to sit down and finish this edition on the topic of Speed. In continuation from last post, we are going to talk about speed and the airplane, or aircraft as a whole, and how speed affects performance and the aircraft’s’ structural integrity, as well as other aspects of the affect’s of speed.

The major reason we fly is to get somewhere quickly. This is not always the case though, as sometimes there are outside influences that conflict with our plans for a quick and safe flight form point “A” to point “B”. This situation is responsible for the term “If you have time to spare, go by air”. There are many variables that come into play. Such as weather, the condition of the equipment, the condition of the crew, the current airport environment, and a multitude of other lesser important variables that can add up to major issues. This last scenario is described as “The Daisy Wheel”. That’s when a series of small events compound into a catastrophic result. There are a multitude of air carrier accidents that have experienced this unfortunate phenomenon. (The current Boeing 737 MAX 8 & 9 series of aircraft are a perfect example). General Aviation is not immune to this concept. In fact, it’s more widely existent because of the simple lack of discipline, good judgment and following published procedures. The major cause of GA accidents is “Gotta Go-itis”. This is that phenomenon that usually ends in severe injury or death. I know what you’re thinking. What does any of this have to do with speed? Well, hold on, I’m getting there.

Flying is very safe provided the aircraft is operated within the parameters in which it was designed, built and maintained. Airplanes do one thing very well, and that is fly. They’re not very crashworthy or resilient to abuse. Things go awry when the structural limitations of the aircraft are exceeded. Aircraft speed restriction is expressed as “Vne”. (Velocity, never exceed. The word Velocity is derived from the French word “Vitesse”, which means  speed or rate). And, is denoted by a Red Line, (radial) on the airspeed indicator. Speed can be easily exceeded in some aircraft very quickly if one is not attentive. For example, a 1965 Beechcraft “S-35” V tail Bonanza with the 300 horse Continental IO-550 cruises high in the “Yellow Arc”, very close to Vne. If you push the nose down without greatly reducing power, you will pass right through the Red Line before you realize it. And, if you’re in the correct environment, you could be very efficient in de-constructing the aircraft in flight. I know people who have flown into thunder storms, and managed to exit the other side and lived to tell about it. The aircraft managed to stay in one piece but was so twisted up, it was beyond economical repair and considered a total loss by the insurance company. Others I’ve known, have been spit out the other side in pieces and obviously didn’t live to tell about their experience. The violent vertical speeds in which the aircraft experiences in that Cumulonimbus cloud, overcomes the structural limitations of the aircraft, and it’s literally torn apart. Vne is exceeded, as well as other induced structural forces, and the results are read in the synopsis section of the corresponding NTSB accident report.

Other speed exceeding events come in a flight regime that exists in CAVU (Clear And Visibility Unlimited) conditions. Operating at the upper end of the Yellow Arc well above published Maneuvering speed, or Normal Operating speed, “Vno” (Velocity, normal operating) in rough air, can also result in severe injury or death. Flying on a clear day can present some unexpected surprises if you don’t know what to expect. Turbulence is a factor than can exist on the CAVU day if the right conditions exist. Flying over different terrain can cause rising and falling air currents, that if you’re not expecting, can cause injuries conducive to a severe hit over the head with a baseball bat. I have been in this situation years ago on a test flight. We were flying over the desert area through the Banning Pass, when we experienced severe up and down drafts. Most people refer to these drafts as “Air Pockets”. There is no such thing unless you’re referring to a vacuum. Having ones seat belt very snug is imperative in avoiding head injuries caused by your padded headset carry over band impacting the overhead tubular structure of the aircraft while experiencing a severe down draft. The victim of this event received an immediate headache that lasted for the rest of the day, which allowed me to log some flight time for the duration of the flight. This event demanded a severe reduction in power, which resulted in a corresponding reduction in forward speed (velocity), down to the lower end of the green arc well into the published maneuvering speed for this particle aircraft. The flight was still akin to being like a frog in a blender, but after the ordeal, the airplane was reusable. As the saying goes, “we cheated death one more time”.

Then there are the tragedies that possibly could have been avoided if the design or a redesign of the original structure was engineered, constructed and altered properly. This topic is derived from my experience walking through the pits at the Reno Air Races. In an attempt to go fast, I witnessed several race teams discussing ways to go faster, without taking the safety factor into consideration. Making the aircraft lighter will indeed increase the speed. It’s the power to weight ratio formula at play here. But, lightness is inversely proportionate to strength, (I don’t care what you say). There is a balance, and I will always chose on the margin of the safety side over a structure that is the most appropriate to the objective of going faster. There are materials that offer both strength and lightness used in aircraft construction, but again they have their place, and without the proper engineering, can lead to catastrophic failure.

I’m going to use the Leeward “Galloping Ghost” tragedy as an example. Now, keep in mind, I’m no expert, and I don’t claim to be. This opinion is based on what I have seen in videos and other forms of media that clearly illustrate the events that lead to the destruction of the aircraft and the death and injury of the parties involved. I have witnessed these race teams at Reno try to obtain the “winning edge” by sacrificing safety over speed. The quest to go fast and win, overcomes the safety aspect of the sport. It’s human nature. Well, “Male” human nature anyway.

The North American P-51 D model that Jimmy was flying on that fateful day, had been around the block quite a few times, and with every new owner, some kind of modification or alteration had been performed on the airframe. Now. it’s impossible to say how much of these mods were or were not “engineered”, but I know how the “experimental” crowd thinks. One aspect of the accident was the inflight  separation of the right elevator trim tab. It is not clear, but it is assumed that the trim tab departed the elevator because of the induced flutter caused by higher speed than the structure was capable of enduring. This event doesn’t seem to be conclusive to the aircraft’s extreme change in attitude, but it could have been a contributing factor. One other observed factor, is that in a series of still photographs, you cannot see Jimmy in the cockpit. Speculations are that the seat collapsed under the extreme positive “G”‘s that the aircraft was experiencing, and forced him to the floor, and with the control stick in his hand, he inadvertently pulled back on it, sending the aircraft in the nose up attitude, it then stalled, and headed toward the ground at nearly 400 plus MPH. It’s hard to say for sure that this is indeed what happened, as there isn’t very clear and concise evidence supporting this possible factor in this tragic event. But, again, I know firsthand that certain safety aspects take a back seat to “keeping it light as possible” in the quest to win. It’s no different in the automobile world.

Hey, I’m all for searching for that competitive edge, but not at the sacrifice of safety. I remember years ago at Oshkosh, one of the performers was landing his Hawker Sea Fury and locked up the brakes and the aircraft ended up on it’s lid. The pilot died from suffocation because he and his crew had removed the roll over structure behind the pilot’s seat for aesthetic reasons. It simply looked better without the roll-over structure. I’m sure he had second thoughts when he was inverted still strapped in his seat with his chin in his chest slowly suffocating to death. It’s just not worth dying for.

In the case of Jimmy Leeward, for me, if I’m clickin’ through the air at 400+ MPH, and something goes awry, I want to know that I have a fighting chance to survive the impending crash. Now, excessive speed isn’t always the culprit that results in your ticket being called. A Piper J3 can kill you just as fast as a P-51 Mustang. Making something safer isn’t always pretty or weight saving. there are penalties or compromises as I call them. Take for example the ‘Coupe. I painstakingly spent hours upon hours fabricating a rollover structure that unnoticeably fit into the windshield frame to strengthen it in the case of a roll-over scenario as there really isn’t much structure there to support any real loads if inverted. Did this safety feature add weight? You bet it did, but not that much. Ironically, with all of the added equipment, this “windshield frame support tube”, the S-Tec two axis autopilot, and everything else, the aircraft weighed in at just under thirty pounds from the original factory weight. We did try to make up for the added amenities by removing all of the antiquated radio equipment and exchanging them for new electronic stuff. The heavier AC-Delco generator was swapped with a modern lightweight alternator and replacing the plywood floor boards with composite honeycomb units. When I was building this aircraft, I kept the weight aspect in mind, but didn’t obsess over it. We have to have certain items and that’s the way it is. Like a fire extinguisher. I have seen many airplanes with a little teeny weenie fire extinguisher in the pouch behind the pilot’s seat or some other unreachable-in-flight spot, because it saves weight. Really? Weight is what your worried about saving with that puny little thing. Fire extinguisher size is directly proportional to time of extinguishing duration. I want as much “time” as I can reasonably get. Five or ten pounds of Halon 1211 is not practical in the cockpit/cabin. But, two to three is. This gives you minutes not seconds of fire fighting time. And, you can give a burst and stop, and possibly have several more bursts of extinguishing agent before you run out. This will give you time to find some real estate and land the aircraft before you’re that smokin’ hole in the ground that gets reported on the eleven o’clock news. Time. That’s what I want. And plenty of it. Remember, it’s better to be on the ground wishing you were in the air, than being in the air, wishing you were on the ground.

So. what have we learned here? Speed is indirectly proportional to weight for the same power. A lighter aircraft of the same model will fly faster on 100 hp. than one that is over nourished.

Saving weight by removing safety items or trimming structural components just to go faster is never a safe practice. Don’t ever sacrifice safety over saving weight.

Until next time, keep the shiny side up!