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Several formal References

1. Intro paper engine-out airplane control

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

14. Review DA 42 AFM

15. Review book Multi-Engine Piston David Robson

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 emergency procedures and airspeed limitations are published in the Airplane Flight Manuals.  Since 1996, more than 500 of such accidents were reported on the Internet alone, causing more than 4,000 casualties.

The cause of these accidents is that the minimum control speed in the air (VMC or better VMCA) of multi-engine airplanes is considered to be a safe minimum speed for maintaining control when an engine fails or is inoperative, including during turns, but VMC(A) is a safe minimum speed for maintaining straight flight only, while banking a few degrees into the good engine when the asymmetrical thrust is maximal.

The accidents could have been prevented if pilots and investigators would have had a bit more understanding on the subject of flight with an inoperative engine, but the pilots are not to blame, knowledge just faded away during the past 50 years in flight and investigator training.
To again increase the level of knowledge of pilots and investigators to a level required to be able to prevent accidents after engine failure, the papers presented below thoroughly explain VMCA, including the conditions under which it is valid and the factors that affect the magnitude of VMCA and therewith performance in-flight. Investigators will also find several analyses of engine failure related accidents.
The papers are written using airplane design books by Dr. Jan Roskam (KU), 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 teaching and training Experimental Test Pilots and Flight Test Engineers, for which download links are provided below (Ref's 10 and 11), or on the Links page (for the full Flying Qualities courses).
In addition, several reviews of other flight and training manuals are provided below, not to apportion blame or liability, but to learn from.

What is VMCA or VMC?

VMCA is explained in an increasing level of detail in the papers #1 to #3 presented below and also briefly on the VMCA page.

On YouTube, a video lecture can be viewed that explains VMCA and reviews two accidents.
A pdf file with slides and script used in this video can be downloaded here.

Papers with background theory

1. Controlling Airplanes after Engine Failure - Tail Design Imposed Limitations

In only 4 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 to get a better appreciation of VMCA.  First published 2008, last updated Jan. 2023.

Download this paper     |    Top

2. Control and Performance during Asymmetrical Powered Flight

For multi-engine rated pilots to learn about the real value of VMCA and engine-out flight, including improved definitions and emergency procedures.

Detailed paper in accordance with the JAA (and FAA) Learning Objectives CPL & ATPL, based on FAR's and EASA CS's and Airplane Design Methods as taught by Aeronautical Universities and on Flight Test Techniques as taught by Experimental Test Pilot Schools.
29 pages, 28 figures, 1.7 MB pdf.  First published January 2012, updated Jan. 2023.

Download this paper     |    Top

3.  Airplane Control and Analysis of Accidents after Engine Failure

For accident investigators, engineering & test pilots, flight instructors and 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 Jan. 2023. 85 pages.

Many accident and air safety investigators, engineering test pilots, flight instructors 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, reason why this gap needs to be bridged to prevent many accidents and fatalities after engine failure in the future, which is the objective of this document.

To the opinion of AvioConsult, the limitations and conditions used during designing and flight-testing a multi-engine airplane are not appropriately passed on anymore to (airline) pilots in manuals and during flight training.  Many pilots, investigators and manual writers just use text out of Airworthiness Standards and Regulations (Part 23, 25) that are intended for designing and for the certification of airplanes, but that are definitely inappropriate for operational use.

This document not only explains airplane control - while the thrust is asymmetrical - but also engine-out climb performance and the many factors that have influence on control and performance.
Five 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.

Included in this document 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.

Pilots will, after reading this document, 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 due to the loss of control while an engine is inoperative.

Airplane accident and air 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.
Accident Investigators and Manual Writers 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.

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 published in the limitations section 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.

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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 charts showing the effect of bank angle and weight on VMCA and on takeoff safety speed V2 are included.  These charts 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 that are also useful for pilots of two- and four-engine airplanes, because it tells what AFMs no longer do. This method can be used for all multi-engine airplanes, provided the required stability derivative data are available. If you download this paper, please also download paper #3.

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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...

Download this review   |    Top

14. Limited Review DA 42 Airplane Flight Manual

Following an accident with a DA 42 airplane in Slovakia on 22 Feb. 2023 during engine-out training (as was spoken of in the local media), AvioConsult became curious whether its Airplane Flight Manual would be correct on the subject of engine-out operations and be in agreement with EASA Flight Test Guides. A limited review was conducted after which the conclusion is: regrettably it's not. This review is loaded with explanations to learn from and to help improve the manual; it is not written to apportion blame or liability. Many remarks apply to flight manuals of other multi-engine airplane types as well.

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Limited Review Book Multi-Engine Piston by David Robson

Many books do not tell the real truth about minimum control speed VMC / VMCA. A few errors found in this book as of 2005.

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The following formal documents were used for writing the papers available on this website.  
A few comment boxes are inserted on the pages of references 2 - 6 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.
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 of the full course books are provided on the Links page. Links to the complete 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.


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