Friday, November 11, 2011

Pilot's Operating Handbooks 101

AppId is over the quota
AppId is over the quota

The term Pilot's Operating Handbook (POH), originated from the US General Aviation Manufacturer's Association who introduced the 'GAMA Specification No. 1' format for the 'Pilot's Operating Handbook' in 1975.

The 'GAMA Specification No. 1' format for the 'Pilot's Operating Handbook' (POH) was adopted in 1991 by ICAO in their Document 9516: Guidance on the Preparation of a Pilot's Operating Handbook for Light Aeroplanes, and is now required for all newly certified aircraft by ICAO member states. Most light aircraft listed initially registered in 1976 or later, have Pilot's Operating Handbooks (POHs) in this format.

POH Standard Format

The GAMA format was designed to enhance safety by providing a standardising ergonomic layout for use in flight.

It is recommended that pilots become familiar with the order and contents of each section, as follows:

Section 1 General: Definitions and abbreviations;
Section 2 Limitations: Specific operating limits, placards and specifications;
Section 3 Emergencies: Complete descriptions of action in the event of any emergency or non-normal situation;
Section 4 Normal Operations: Complete descriptions of required actions for all normal situations;
Section 5 Performance: Performance graphs, typically for stall speeds, airspeed calibration, cross wind calculation, takeoff, climb, cruise, and landing;
Section 6 Weight and Balance: Loading specifications, limitations and loading graphs or tables;
Section 7 Systems Descriptions: Technical descriptions of aircraft systems, airframe, controls, fuel, engine, instruments, avionics and lights etc;
Section 8 Servicing and maintenance: Maintenance requirements, inspections, stowing, oil requirements etc.;
Section 9 Supplements: Supplement sections follow the format above for additional equipment or modification;
Section 10 Safety Information: General safety information and helpful operational recommendations which the manufacturer feels are pertinent to the operation of the aircraft.

Other Formats and Terms for the POH

The manufacturer's handbook is also often referred to as the approved Aircraft Flight Manual (AFM), or Aircraft Operating Manual (AOM) by aviation authorities, since it is a manual containing all the information relevant to flight operations.

Prior to 1976, many light aircraft manufacturers, including Cessna, referred to the manfacturer's operating handbook as an Owners Manual, using the same convention as a motor vehicle, and many of these manuals contained no more information than that provided for your motor vehicle.

A copy of a POH that is not issued to an aircraft is sometimes called a 'Pilot's Information Manual' and can be a very useful addition to one's home reference library.

Larger aircraft normally refer to the POH as a 'Flight Crew Operating Manual' (FCOM), being a larger document, often in a number of volumes, which may be used by a flight engineer as well as pilots. Larger aircraft require a different format because of the larger amount of content contained in the operating handbooks and because of the different methods of operating in multi-crew environments.

What To Do When There is No Information Specified in the POH?

The is the master document for all flight information, and pilot's may not deviate from the POH unless specific approval has been granted by the relevant aviation authority for such deviation. However there are many situations which are not catered for in the POH.

Often there are normal situations where the POH does not specify how the operation should be conducted, yet, unless specified as a limitation, the situation is not forbidden.

One common example is performance factors for operation on surfaces other than paved or dry grass runways. The operations are allowed, but no figures are provided for the multiple of other factors that can affect takeoff and landing distances, for example soft sand, rough dirt, long grass, wet surfaces, standing water, slush or snow. The UKCAA has published a list of performance modifications (link) to allow for non-POH situations, and, in the absence of guidance from your own aviation authority or from the aircraft operator's approved company operations manual, it is recommended that these should be used.

Another common omission on early Owners Manuals is emergencies and abnormal operations, for example 1960's and earlier Cessna Owners Manuals have no information about emergency procedures except for glide performance graphs. Since we all know this is not the limit of failures, this leaves a pilot faced with two choices, to apply common sense and techniques learned on similar types during training, or to use the procedures specified in later model POHs for the same type, bearing in mind any differences.

Wherever in doubt, seek the guidance of the local aviation authority operations department.

Updating a POH

It is important to remember that it is issued to a specific model and serial number, and includes all applicable supplements and modifications.

The POH is approved by the aviation authority during type certification, and issued to an aircraft when it is manufactured as part of the initial airworthiness certificate. Thereafter, the operator, in conjunction with the maintenance provider, must ensure the POH is kept up to date

Changes to the POH will be one or two types:

- Those issued by the manufacturer due to new discoveries in safety practices;
- Those required by the inclusion of post manufacture modifications.

The first type, which will normally come in the form of an aeronautical directive or service bulletin, will contain instructions for insertion and removal of the effected pages along with a new list of effective pages.

The second type will come in the form of a 'POH Supplement'. The POH supplement forms part of the Supplemental Type Certificate (STC), which is issued to all approved aircraft modifications by the aviation authority in the state of manufacture.

A POH supplement which does not affect handling is a straight forward affair, since it is simply inserted in section 9 of the POH, with an inclusion in the table of contents, or for non GAMA format POHs, inserted at the end of the POH or aircraft document folder.

Where a POH supplement has characteristics that affect aircraft operation, for example STOL kits or engine upgrades, there is a more complicated and important process which is normally not specified clearly in the STC documentation. Because these characteristics can change parts of the normal operating, limitations, performance, and emergencies sections, these sections also need to be modified. Wherever a STC supersedes data in these sections, the changed information must be crossed out and a note referring to the supplement included. Where possible a copy of the information from the supplement should also be included in the relevant section for more ergonomic reference. If this is not done, a pilot can easily be misled by referring to the incorrect information in the main part of the POH without realising it has been changed by the supplement. If yoou or your maintenance provider are unsure about the procedure, refer to your local aviation authority's airworthiness section for guidance.

Type Transition Training and Ground Reference

For home study, ground training, a good training manual should be used, in conjunction with a Pilot Information Manual, which will ensure all the background information on a type is obtained, whilst becoming familiar with the Pilot's Operating Handbook.

For reference prior to flight, only the approved POH from on board the aircraft you are going to be flying, should be used. It should be obvious to you now, that even if you have a copy of a POH for the same model, the aircraft you are flying may have supplements for modifications and additional equipment which affect operation.

About the Author:

Danielle Bruckert is a co-author of the popular Cessna Training Manual series, available for the Cessna 152, Cessna 172, Cessna 182, Cessna 206, and Cessna 210, http://www.redskyventures.org/.

To provide support for this training series and other text books she writes, she has created a large resource of free downloadable pilot's operating handbooks, maintenance manuals and pilot resources, for Cessna and other aircraft, available at http://www.redskyventures.org/free_stuff.php.

Red Sky Ventures asks for your help in collecting more POHs, to improve aviation safety through shared knowledge.

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