Introduction

All across the globe, accidents with both small and big multi-engine airplanes continue to happen quite frequently following the failure of an engine during takeoff, go-around, approach for landing and during training, despite the fact that all airplane types are thoroughly flight-tested and operational limitations are published in the airplane flight manuals.  Since 1996, more than 300 accidents were reported on the Internet causing 3,100 casualties. 
Download the list of engine failure related accidents here.

Multi-engine airplanes are designed, flight tested and certified to continue to fly safely after engine failure or while an engine is inoperative.  After reviewing many accident investigation reports using the knowledge gained at the USAF Test Pilot School, it was noticed that most pilots and accident investigators explain and use the minimum control speed in the air (V_MCA or V_MC) in a different way than airplane (tail) design engineers, experimental test pilots and flight test engineers do; the important and life-saving conditions that come with V_MCA are obviously not known anymore.  This difference in interpretation has, to the opinion of AvioConsult, resulted in many catastrophic accidents caused by the loss of control and/or performance after engine failure and also has resulted in incorrect and incomplete conclusions and recommendations in accident investigation reports.  

What is V_MCA or V_MC? Click here to open a separate window with explanation.

In order to bridge the obviously existing gap between airplane design & flight-test and airplane operations, a number of papers are made available for download below that explain the real value of seven types of V_MC and the important conditions that are required for the Flight-Manual-published V_MCA to be valid, in order to prevent accidents after engine failure in the future and to learn how to analyse accidents after engine failure.  

References:

- On-line One Engine Inoperative Trainer, University of North Dakota, click here.
- Test Pilot School books and manuals -  not accessible to the public.
- Dr. Jan Roskam, Airplane Design, University of Kansas, DARcorporation, click here.
- FAA Federal Aviation Regulations Part 23 and Part 25, click here.
- FAA Flight Test Guide, AC23-8C, click here.
- FAA Flight Test Guide, AC25-7B, click here.
- EASA Certification Specification 23, incl. Flight Test Guide, page 196, click here.

Papers background theory 

1.  Controlling Airplanes after Engine Failure - Tail Design Imposed Limitations
In only 3 pages, the most important operating limitations for flight with an inoperative engine, that are consequences of the methods used to design the vertical tail of a multi-engine airplane and the experimental flight test to determine minimum control speed in the air (V_MCA), are briefly explained. 

Download this paper (for free)|  Top

   Also available in the Dutch language, below.

Detailed paper in accordance with the JAA (and FAA) Learning Objectives, FAR's and EASA CS's for Multi-engine Rated Pilots, CPL & ATPL.  Based on Airplane Design Methods as taught by Aeronautical Universities and Flight Test Techniques as taught by Experimental Test Pilot Schools. 28 pages, 26 figures, 2 MB pdf. 

Download this paper (temporarily for free)

For accident investigators, engineering & test pilots, manual and book writers, flight-instructors and pilots who want to know it all. 
May 2012.   

Many accident investigators, engineering/ test pilots and Flight Manual writers explain and use the V_MCA of an airplane not in the same way as airplane design engineers, experimental test pilots and flight test engineers do. 
To the opinion of AvioConsult, the limitations and conditions used during designing and flight-testing a multi-engine airplane are not appropriately passed on to (airline) pilots in manuals and during flight training.  Many pilots,  investigators and manual writers just use text out of Regulations (Part 23, 25) that are intended for designing and for the certification of airplanes, but definitely not for their operational use.  

This paper, written by a Test Pilot School graduate, explains airplane control while the thrust is asymmetrical and also engine-out climb performance and the many factors that have influence on control and performance.  Seven types of V_MC are discussed, as are the flight-test methods to determine these minimum control speeds (V_MC's).   The conditional safety of V_MCA and of the derived V₁ and V₂ are explained, because inadequate accident reports show this is required.  A few incorrect definitions of V_MCA in Flight and Operating Manuals are discussed as are inappropriate engine emergency procedures. Training and demonstration of V_MCA in-flight, including cautions, are included as well.

Included in this paper are analyses of 6 engine failure accidents that actually happened. Three of these fatal accidents (EMB-120ER, Saab SF-340B, Jetsream 4100) are analysed step by step using Flight Data Recorder (FDR) data as illustrated in the adjacent figure.   After reading this 71-page paper, airplane accident investigators will be able to improve the analysis of airplane accidents following a propulsion system malfunction and write much better and appropriate conclusions and recommendations in accident investigation reports. These reports will become much more valuable for preventing propulsion system malfunction related accidents and incidents in the future.

Pilots will understand the conditions for which V_MCA, V_R and V₂ are valid much better, will improve airplane control after engine failure, know how to achieve best climb performance and will never crash anymore due to the loss of control while an engine is inoperative. 
Manual and procedure writers will understand V_MC's much better and use the gained knowledge to improve definitions of V_MC's and engine failure procedures in Flight and Operating Manuals.  
All readers will understand engine-out performance and the real value of the V_MC's that are listed in all Flight Manuals of multi-engine airplanes, as well as the conditions for which V_MC's are valid. 

Reading and understanding this paper will prevent the loss of control 
and performance after propulsion system malfunctions 
in the future.

To assist in reading FDR data plots more accurately, print either of these free grid sheets on a transparent sheet using a laser printer: Grid sheet A4 format Grid sheet Letter format   Top

4. Imperfections and Deficiencies in FAA and EASA Regulations 
A paper that resulted from the research for the papers presented above. It presents and explains many errors found in aviation regulations that might lead to accidents after engine failure and includes ready-to-copy suggestions for improvement. 

This paper is also available from the Flight Safety Foundation on the CD-ROM that contains all EASS 2006 papers. 

Comments on Flight  and Training Manuals

The FAA Course Notes Multi-Engine Safety Review that is presented on the FAASafety website, was reviewed by AvioConsult using the knowledge of experimental flight testing.  The Course notes - as of Aug. 2012 - do not agree with Flight Test Techniques used to determine V_MCA as taught at Test Pilot Schools and as published in FAA Flight Test Guides in Advisory Circulars.  This paper presents many suggestions for improvement which are definitely required to improve the Notes and therewith flight safety. 
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 Airplane Flying Handbook FAA-H-8083-3A, Chapter 12 "is devoted to the factors associated with the operation of small multi-engine airplanes".  This Chapter was also reviewed by AvioConsult using the knowledge of experimental flight testing.  This Chapter - as of Aug. 2012 - regrettably does neither agree with the design methods for sizing the vertical tail of multi-engine airplanes nor with the Flight Test Techniques used to determine the engine-inoperative flying qualities, including V_MCA, as taught at Test Pilot Schools and even as published in FAA Flight Test Guides in Advisory Circulars.  Besides a review, this paper presents many suggestions for improvement which are definitely required to improve the transition to multi-engine airplanes and prevent accidents after engine failure.  
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January 2013

This document was referenced in the accident report of a PA-31P-350 in Bankstown, 15 June 2010 and reviewed.  Although all ingredients of flight with an inoperative engine are included, somehow it became clear that V_MCA and V_MC and the conditions that apply with these minimum control speeds were not clear to the authors, and hence will not be understood by pilots, resulting in accidents.  Improvement is definitely required, therefore this paper also presents suggestions for improvement. 
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