Machines | Airplane Accidents after Engine Failure - Real Value of Vmc
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Improperly used Minimum Control Speed Vmc Killed Thousands. During the past 25 years, more than 360 engine failure related accidents with multi-engine airplanes were reported on the Internet alone, causing more than 3,200 fatalities. Many, if not all of those accidents happened because the pilots were not aware anymore of the real value of the air minimum control speed Vmc(a) and the flight-constraints that come with it, as a consequence of both the airplane design and the flight-test methods and conditions. The mishap pilots operated their airplanes after engine failure in a way that the airplanes were not designed to be capable of. Accident investigators were obviously not aware of this either. This video briefly analyses two accidents, explains the real value of Vmc(a) and presents tips to improve flight safety. After viewing this video, pilots will be able to return home safely following an engine failure, and airplane accident investigators will improve their search for the real cause of engine failure related accidents. The definitions of the minimum control speed (Vmc) of multi-engine airplanes in airplane flight manuals, flying handbooks and pilot training textbooks are usually copied out of the Federal Aviation Regulations 23 and 25 §149 or equivalent. These Regulations however, are for the design, certification and (experimental) flight-testing, but are inappropriate, even deficient for flight operations. The engine emergency procedures in flight manuals and checklists fail as well. Airplane Flying Handbooks, issued by aviation authorities, present theory about Vmc(a)and about flight with a failing or inoperative engine that does not concur with (their own) Flight Test Guides, or that was copied from uneducated sources . This video was made by a Test Pilot School (TPS) graduate and explains Vmc(a) and its constraints, as it is still taught at leading Aeronautical Universities and at the experimental Test Pilot Schools around the globe (for which the entry level is a MSc or BSc degree + entry exam). Many pilots must be shocked during viewing. They'll find it very hard to believe that Vmc is not a minimum control speed as they learned and always thought, but only a minimum speed for maintaining straight flight. Their lives and that of their pax were at stake. References are provided to reliable background information, including the formal FAA and EASA (experimental) Flight Test Guides and the Airplane Design series of books by Dr. Jan Roskam, KU. TPS graduates are also reliable references. This video makes it very clear that pilot manuals and -procedures need to be reviewed frequently by someone with a higher level engineering knowledge of the subject matter than pilots and certification pilots and writers, to prevent the correct knowledge from fading away, as happened in this case, during the past 50 years.
Comments
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Mr. Horlings, would you please respond to this post? I would like you to see a video of what I believe is a VMC Roll. P.S. I worked at the USAF Test Pilot School as a dispatch specialist. This was back when El Onizuka was an instructor at the facility.
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Thank you very much for this. Brilliant, concise, and thoroughly helpful.
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You wrote: "This video is not at odds with what multi engine pilots are taught". I agree but would change the subject: What multi-engine pilots are taught is no longer at odds with Airplane Design as taught by Dr. Jan Roskam (KU), with the FAA Flight Test Guides in Advisory Circulars and with the papers by a flight test expert on the downloads page of website www.avioconsult.com. The real problem, and the cause of many accidents, is what pilots do not learn anymore about Vmc(a), like the conditions under which Vmca is safe to fly.
When the small bank angle is not being maintained, not only the drag increases (sideslip) but also Vmc (Dr. Jan Roskam, KU: "Vmca and Performance are tied together by the bank angle"). Therefore the technique to be used by pilots after engine failure is to maintain straight flight while banking 5 degrees away from the failed engine (The exact bank angle should be provided by the manufacturer with Vmc(a) data). The vertical tail of a multi-engine airplane is not designed, is not large enough, to be able to maintain control (and performance) for any other bank angle when the airspeed is close to or equal to Vmc(a) after failure of any engine, critical or non, while the opposite engine is set to provide max. thrust. During experimental flight testing to determine Vmca and evaluate the controllability during flight and during go-around, we apply this technique and we don't crash.
Lack of adequate rudder increases the actual Vmca, i.e. the Vmca that the pilot experiences in-flight. The E120 pilot allowed the heading to walk away from the initial heading while he had ample rudder available, hence did not maintain both heading (straight flight) and a small bank angle.
Vmc is a safe airspeed provided a pilot understands and applies the conditions that come with it. The Vmc published in flight manuals is the worst case Vmc that a pilot will ever experience in-flight. It is safe, but only if he or she maintains the heading and the small favorable bank angle. Otherwise Vmc will increase above the IAS and the dead engine will turn into a killing engine. These important conditions were and are regrettably not published in pilot manuals and course books anymore during the past 50 years. Exceptions: Lockheed C-130 manuals and old DC-8-63 manuals.
Five degrees of bank would have saved the E120 flight for sure; it's undisputable physics: the balance of forces and moments. Neither the flight instructor, nor the pilot was obviously aware of the real value of Vmca, because there are probably no course books anymore that are right on this subject. Most, if not all pilot course books are not in agreement with Roskam and the Flight Test Guides issued by (an other department of) the FAA, that are also used at Test Pilot Schools. Even FAA-H-8083-3a/b Chapter 12, Transition to Multi-engine Airplanes, is definitely not right. Please refer to the downloads page of the mentoned website, download #8.
I really wish you could show me a ME rating course book in which Vmc is correctly explained.
By the way, Vyse is not safe either to turn either when one engine is inoperative and the other is at max. thrust. -
While the analysis is interesting and on point, using the second example to illustrate the point is off. If the aircraft is certified with an auto feather and it was not put in simulated flight to represent these conditions, then likely no technique would allow it to maintain required speed on the V1 cut. The E120 pilot did infact attempt to raise the left wing a couple of times, but his lack of full rudder thwarted his efforts.
Also the VMC definition is used because there is a need for pilots to understand the factors used to determine VMC. I know of no multi pilot that assume Vmc is a "safe" airspeed to use. It is drummed into every student that Vmc is that, the minimum speed, lower and you will lose control. Vyse is the airspeed target.
So no 5 degrees of bank would have saved either of these flights. There is a risk involved with flight below Vmc as in the first example, and there is risk involved with improper configuration for V1 cuts and simulated single engine flight.
The video is informative, but unlike the assertions, it is not at odds with what multi engine pilots are taught. Airspeed =Control=Life. -
Awesome. There is so much we light twin drivers take for granted.
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Excellent presentation.
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A great analysis and very thought provoking. Thanks for your time and efforts.
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Terrific and scholarly presentation of a subject that should be much more widely taught and understood. Thank you.Jonathan Friedman ATP, CFI, MEI
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Absolutely perfect explanations and demonstraions!!! This information should be like a "bible" for twin engine pilots...I'm an electric/electronic engineer(doing my final practices to get the degree) but aviation is my passion. This is one of the best videos I ever watched. Engineers calculate EVERYTHING with high enough safe margins, but I certainly think that the TO speed is very near the Vmca, I believe 5% is a very low margin given the fact that when an engine fails so close to the ground and with a high AOA the speed will drop immediately, and probably for some airplanes this TO speed is almost the "wings leveled" Vmca. Why don't the flight manuals publish a higher TO speed, "just in case"? Why most of the pilots have to investigate on their own to get te safest speeds?? Shouldn't the wings leveled Vmca be published to have a better safety margin?
I'm sure some instructors will add this 10kt safe margin but I believe in general there is also an excess of comfidence on the engines' performance and piloting skills that certainly leds to catastrophic accidents. -
i was in Darwin Australia when that Embrear crashed
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Excellent presentation. I will be passing this to all the pilots I know.
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Mr. Avio, Just brilliant. You have summed it up brilliantly. Thank You.
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This video should be required viewing for pilots (up there with the American Airlines Advanced Aircraft Maneuvering Program series).
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Excellent video. Some new information for me. Thank you so much for posting this.
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Thank you Harry. You are saving lives.
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Thanks for posting this video. Very good presentation.
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Excellent! Thank you. Everything you said is correct. Some questions from me: In the first crash example, would it not have been very difficult for a pilot to recognize the sudden failure of the right engine unless the pilot was staring at the engine gauges? Certainly the pilot would have felt or observed the yaw to the right after it began to occur but in this example, wasn't that too late? However, if the pilot had rotated at 1.05 Vmca +10 knots as you say, he would have had more airspeed, and perhaps an extra two seconds to figure this out and attempt to stop the yaw. However on that aircraft, and in your example the pilot did not appear to have had sufficient time to process thought to reduce maximum thrust on the operative engine to prevent the roll, while at the same time mentally processing the other multi-engine emergency procedures - banking into the operative engine not more than 5 degrees, controlling the yaw, gear up, flaps up. Do you agree or am I incorrect? I fly a Seneca II and am applying your lesson IMMEDIATELY to my flying. Thank you for sharing your important analysis.
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Thanks for your comment. It supports the conclusion that control after engine failure, and therewith the appreciation of the real value of Vmca, got less and less attention during the past 40 - 50 years. I've old DC-8-63 and current C-130 manuals, besides Test Pilot School manuals, that present the right stuff on the subject. Most FI's and authorities who I talked to, told me "never heard of it, cannot be right what you're saying" (they are younger than you and I). How do we get to teach all multi-engine pilots the real value of Vmca again, and the do's and don'ts that come with it? Pilots (and their pax) don't want to get killed, do they?
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When I was getting my multi engine rating 37 years ago my instructor made me experience this loss of control at 5000 feet above ground and allowed the plane the completely roll over and note the speed when it began Beech Baron e55. In that experience I never forgot how useless the controls were. and I always took it upon myself to practice whenever got the chance.