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Several formal References

1. Three page intro paper

2. Control and performance during asymmetrical powered flight

3. Airplane Control and Analysis of Accidents after Engine Failure

4. Imperfections in Regulations

5. EASS: Staying alive with a dead engine

6. The effect of Bank Angle and Weight on VMCA

7. FAA Multi-engine safety review

8. Review of FAA-H-8083-3A Chapter 12, Transition to Multi-engine Airplanes

8a. Flying Light Twins Safely

9. Review of CAAP 5.23-2(0)

10. PA-44 docs

11. B737-200

12. Safety Forum Brussels 2019, Paper on Safety Procedure Development

13. Review ATR-72 AFM

Copyright and Liability

Publications by AvioConsult for download

Introduction Downloads Page

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 engine-out training, despite the fact that all airplane types are thoroughly flight-tested and airspeed limitations are published in the Airplane Flight Manuals.  Since 1996, more than 480 of such accidents were reported on the Internet alone, causing more than 4,045 casualties.

The cause of these accidents is that the minimum control speed in the air (VMC or better VMCA) is considered to be a safe minimum speed for maintaining control when an engine is inoperative, but VMC(A) is not a safe minimum speed for controlling the airplane, but for maintaining straight flight only, when the asymmetrical thrust is maximal.

Airplane design engineers apply a bank angle of a few degrees (max. 5°, i.a.w. FAR 23.149, 25.149 and equivalent) away from the inoperative engine during sizing the vertical tail for the sideslip to be minimal at VMC(A).  The small bank angle reduces the required size of the vertical tail, which then can be made smaller, hence cheaper and less heavy. While maintaining the small bank angle, the sideslip / drag is minimal and hence, the remaining climb performance is maximal. And last but not least, the VMC(A) while maintaining straight flight with the small 5° bank angle is lower, safer than with the wings kept level or at other bank angles. 
The VMC(A) that is published in Flight Manuals is determined during flight-testing while maintaining both this small bank angle and straight flight (i.a.w. ref's 2 - 4 and 10 and 11 below).  Maintaining wings level or any other bank angle (i.e. during turning) increases both the actual VMCA and the drag considerably.

Consequently, the vertical tail of a multi-engine airplane is usually not designed large enough for maintaining control during turns at airspeeds as low as VMC(A) while an engine is inoperative and the power setting on the opposite engine is maximum.  During turns at asymmetrical power, performance will be lost due to the increase of sideslip or even fin stall, and control might be lost.  Loss of Control In-flight cannot be prevented at low airspeeds when a high asymmetrical thrust setting is maintained.  It is this knowledge that might be lost during the past 50 years.

In order to bridge the obviously existing gap in knowledge of airplane control after a propulsion system malfunction between airplane design & flight-test and airplane operations & accident investigation, a number of papers are made available for download that explain the real value of the seven types of VMC and the important conditions that are required for the Flight-Manual-published VMC(A) to be valid, in order to prevent accidents after engine failure in the future and to improve the analysis of accidents after engine failure.

A correct VMCA (or VMC) definition for pilots would be:

VMCA is the minimum speed for maintaining straight flight only when an engine fails or is inoperative and the corresponding opposite engine is set to provide maximum thrust, provided a bank angle is being maintained of 3 to 5 degrees (exact number to be provided by the manufacturer) away from the inoperative engine.

The papers presented below are written using airplane design books as used by aeronautical universities, the formal FAA and EASA Flight Test Guides (Ref's 2 - 4 below) and the Engine Out or Asymmetrical Power Courses used by formal Test Pilot Schools for the training of Experimental Test Pilots and Flight Test Engineers (Ref's 10 and 11 below; see also the Links page).

What is VMCA or VMC?

A 42 min. video lecture, in which the real value of the minimum control speed airborne (VMCA) is explained as taught at all formal Test Pilot Schools and most aeronautical universities. Click here to start the video from the beginning, or follow direct links to the subjects:

Control after Engine failure
Limits due to tail design
Effect of Bank angle and weight
Critical Engine
Flight testing VMCA

Deficient VMCA Definition
Improved VMCA Definition
Takeoff speed
Accident EMB-120ER analyzed
Do's and Don'ts when OEI

A pdf file with slides and script used in this video can be downloaded here

Click here to open a separate window with explanation on VMCA or download and read the formal FAA and EASA Flight Test Guides and FAR and CS § 23.149 (and 25.149), the VMCA paragraphs of which are listed in and downloadable from the list of formal References below. 


The following formal documents were used for writing the papers available on this website.  
A few comment boxes are included on some of the pages for clarification:

1.   On-line One Engine Inoperative Aerodynamics, University of North Dakota, visit.
2.   FAA Flight Test Guide, AC23-8C, pages on VMCA testing, download.
3.   EASA Certification Specification 23, Flight Test Guide , VMCA testing, download.
4.   FAA Flight Test Guide, AC25-7C, pages on VMCA testing, download.
5.   FAA Federal Aviation Regulations Part 23.149 on VMCA, download.
6.   EASA Certification Specification § 23.149 on VMCA, download.
7.   FAA Federal Aviation Regulations Part 23, 25, etc., visit.
8.   EASA Certification Specification 23, click here. All CS's, visit.
9.   Airplane Design, Dr. Jan Roskam, University of Kansas/DARcorporation, visit.
10. US Naval Test Pilot School, Flight Test Manual 106 Chapter 6 Asym Power, pdf, download.
11. USAF Test Pilot School, ADA170959 Ch. 11 Engine-Out Theory, pdf, download.

The US Naval and Air Force Test Pilot Schools have approved their course books for public release; links for download are provided on the Links page. Links to the full Flight Test Guides are provided there as well. In addition, all graduate Experimental Test Pilots and Flight Test Engineers of the major Test Pilot Schools in the USA, UK and FR will be able to confirm that the papers presented on this website are indeed in accordance with flight test techniques and guides.

Papers with 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 the minimum control speed in the air (VMCA), are briefly explained.  First published 2008, last updated Nov. 2020.

Download this paper

Also available in the Dutch language here.     |


2.  Control and Performance during Asymmetrical Powered Flight

For multi-engine rated pilots. 

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 on Flight Test Techniques as taught by Experimental Test Pilot Schools.
28 pages, 26 figures, 2 MB pdf.  First published January 2012, updated Sept 2022.

Download this paper

     |    Top

3.  Airplane Control and Analysis of Accidents after Engine Failure

For flight instructors and for accident and air safety investigators

For accident investigators, engineering & test pilots, manual and textbook writers, flight-instructors and pilots who want to know it all. This paper is a bit more scientific. 
Published May 2012, updated Sept. 2022. 79 pages.

Many accident and air safety investigators, engineering/ test pilots and Flight Manual writers explain and use the VMCA of an airplane not in the same way as airplane design engineers, experimental test pilots and flight test engineers do. This knowledge gap is the real cause of many, if not all, accidents after engine failure.
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 are inappropriate for operational use.

This paper, written by a Test Pilot School graduate, explains not only airplane control - while the thrust is asymmetrical - but also engine-out climb performance as well as the many factors that have influence on control and performance.  Seven types of minimum control speed (VMC) are discussed, as are the flight-test methods to determine these.
The conditional safety of VMCA and of the derived VR and V2 are explained, because inadequate accident or safety reports show this is required.  A few incorrect definitions of VMCA in Flight and Operating Manuals are discussed as are inappropriate engine emergency procedures. Training and demonstration of VMCA in-flight, including cautions, are included as well.

FDR data plot

Included in this paper are detailed analyses of 6 engine failure accidents that actually happened. Three of these fatal accidents (EMB-120ER, Saab SF-340B, Jetstream 4100) are analysed step by step using Flight Data Recorder (FDR) data as illustrated in the adjacent figure.

After reading this paper, airplane accident and safety investigators will be able to improve the analysis of airplane accidents caused by 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 VMCA, VR 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 VMC's much better and use the gained knowledge to improve definitions of VMC's and engine failure procedures in Flight and Operating Manuals.
All readers will understand engine-out performance and the real value of the VMC's that are listed in all Flight Manuals of multi-engine airplanes, as well as the conditions for which VMC's are valid. 

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

Download this paper  |  Top

Required Data for Investigating Engine Failure Related Accidents

Manual Writers and Accident Investigators may find this list of use for verifying whether Flight and Ops Manual data on engine-out flight are complete, and for making sure all data is available for Engine Failure Related Accident Investigations and Analyses.

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

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 imperfections found in aviation regulations that might lead to accidents after engine failure and includes ready-to-copy suggestions for improvement.

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5. Staying Alive with a Dead Engine

A paper presented to the European Aviation Safety Seminar of the Flight Safety Foundation in Athens, Greece in March 2006. The paper addresses the 4 errors that can be found in the definition of VMCA in the Flight Manual of almost all airplanes and explains that there is an important condition for both the minimum control speed VMCA and the takeoff safety speed V2 to be valid.

Download this paper    |    Top

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

6. The Effect of Bank Angle and Weight on VMCA 

In the papers presented above (1, 2 and 3), a few graphs showing the effect of bank angle and weight on VMCA and on takeoff safety speed V2 are included.  These graphs were calculated using a prediction method that is also used by experimental test pilots and flight test engineers before conducting the flight-tests to determine VMCA in order to learn about limitations, etc. that might be encountered during the test flights.  This paper presents the prediction method and includes a few data figures.  This method can be used for all multi-engine airplanes, provided the required stability derivative data are available. 

Download this paper    |    Top

Review of Flight and Training Manuals

7. FAA Multi-Engine Safety Review

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 VMCA as taught at Test Pilot Schools (ref's 10 and 11 above) and as published in FAA Flight Test Guides in Advisory Circulars (references 2 and 4 above).  This paper presents many suggestions for improvement which are definitely required to improve the Notes and therewith flight safety. 

Download this paper with recommendations for improvement    |    Top

8. FAA-H-8083-3A/B, Chapter 12, Transition to Multi-engine Airplanes

Airplane Flying Handbook FAA-H-8083-3A/B, 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, as taught at aeronautical universities, nor with the Flight Test Techniques used to determine the engine-inoperative flying qualities, including VMCA, as taught at Test Pilot Schools (ref's 10 and 11 above) and not even as published in FAA Flight Test Guides in Advisory Circulars (ref's 2 and 4 above).  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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8a. Flying Light Twins Safely. FAA-P-8740-66.

This publication provides the aviation community with safety information, but must be improved to really increase safety and reduce the rate of engine failure related accidents. The recommended improvements are included in text boxes.

Download this paper with recommendations for improvement   |  Top

9. CASA CAAP 5.23-2(0), Multi-engine Aeroplane Operations and Training.

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 VMCA/ & VMC and the conditions that apply with these minimum control speeds were not clear to the authors of the accident report, and hence will not be understood by pilots, resulting again in accidents.  Improvement is definitely required, therefore this paper also presents suggestions for improvement.

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10. PA-44-180 Seminole documents

A limited review of PA-44-180 Seminole documents, as used by flight schools (and by other PA-44 owners).  It should also be useful to operators of other multi-engine airplane types.

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11. Boeing 737-200/300/400 Flight Crew Training Manual

A limited analysis of the Engine Failure Takeoff Procedures in the Boeing 737-200/300/400 Flight Crew Training Manual.  
This analysis was written following a review of the accident investigation report of the accident with an Algerian 737 on 6 March 2003.

Download this analysis   |    Top

12. Safety-Critical Procedure Development Requires High Level Multi-Disciplinary Knowledge

AvioConsult was invited to present this paper during the Safety and Procedures Forum of Eurocontrol in Brussels, 4 - 5 June 2019, about inappropriate control speed definitions and engine emergency procedures in airplane flight manuals and multi-engine course books, and why multi-disciplinary knowledge is required to improve.

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The 30 min. presentation was recorded on video, view here. A pdf with the PowerPoint slides can also be downloaded from SKYbrary here.

The PowerPoint presentation is also available for download here. A few more slides were added. You should enable the macros for the animations to work properly. To reduce the size of the file, the two videos are not embedded, but accessible via external links.

13. Critical Review ATR-72 Airplane Flight and Performance Manuals

Several ATR pilots asked AvioConsult to review their manuals on the subject of engine-out operations, after having read the papers on this website. They suspected the takeoff and go-around speeds to be too low. Not only the AFM was critically reviewed, but also the ATR Performance Guide. The conclusion is that V2, VFTO and Go-around speeds are indeed too low and are not calculated as required by EASA and FAA Regulations. The cause might be that the real meaning of VMCA, and the flight restrictions that come with it, are not known to the performance engineers and manual writers. To the opinion of AvioConsult, the manuals were not written with care. These conclusions also apply to the ATR FCOM and QRH. Convince yourself, and...

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