Autorotation Training

1 PURPOSE

The purpose of this advisory circular (AC) is to describe enhanced guidelines for autorotations during helicopter flight training. The Federal Aviation Administration (FAA) has found a need to raise awareness of the risks inherent in performing autorotations in the training environment, and in particular, 180-degree autorotations. In this AC, the FAA recommends procedures that will mitigate safety risk during autorotations. This information is intended to supplement information about autorotation training found in the current editions of the Helicopter Flying Handbook (HFH), FAA-H-8083-21, and the Helicopter Instructor’s Handbook (HIH), FAA-H-8083-4. This AC is not mandatory and does not constitute a regulation. This AC describes an acceptable means, but not the only means, of conducting autorotation training for proficiency or in consideration of the requirements to be issued an Airman Certificate under Title 14 of the Code of Federal Regulations (14 CFR) part 61. You may use alternate methods for training if you establish that those methods meet the requirements of the HFH and FAA practical test standards (PTS).

2 CANCELLATION

AC 61-140, Autorotation Training, dated May 23, 2013, is canceled.

3 AUDIENCE

This AC applies to all persons involved in helicopter flight training, including flight instructors, Designated Pilot Examiners (DPE), and FAA aviation safety inspectors (ASI). All pilots involved with autorotation training are strongly encouraged to review the information in this AC and apply the techniques as appropriate.

4 RELATED READING MATERIAL

The FAA’s principal guidance on autorotation can be found in the current edition of the HFH, FAA-H-8083-21. This AC supplements and expands the guidance from the HFH.

5 BACKGROUND

5.1 Helicopter Accidents

The U.S. Joint Helicopter Safety Analysis Team (JHSAT) Compendium Report (2000, 2001, and 2006) shows that training continues to be one of the top operational categories of helicopter accidents in the United States, representing 17.9 percent of all accidents. Of the 523 helicopter accidents reviewed, failures in autorotation training were noted in 68 accidents, or 13 percent. Furthermore, at least six accidents within the previous 8 years of issuance of this AC involved a National Transportation Safety Board (NTSB) probable cause as “180-degree autorotations.” Although this is less than 1 percent of accidents in this time period, this advanced maneuver requires attention in an effort to reduce all helicopter accidents. This supports the International Helicopter Safety Team (IHST) initiative of an 80 percent accident rate reduction by 2016.

5.2 Common Safety

This AC follows IHST recommendations on autorotation training and is designed to address the identified mistakes causing a significant number of helicopter accidents in the training environment. The AC addresses the common safety issues in this segment of training. Autorotation training procedures and practices have not been specifically addressed in prior ACs. This AC promotes the recommendations of the IHST for autorotation training and is designed to address the identified errors that cause a significant number of helicopter accidents in the training environment.

5.3 Elevation of Accident Rate

In 2011, after evaluating 3 years of helicopter accident data, the FAA and IHST recognized an unacceptable increase in the helicopter accident rate. Autorotation during actual or training/instructional autorotations and in actual emergencies was an occurrence category for 32 percent of those accidents, and the IHST developed recommendations that it felt could be employed to reduce risk in helicopter autorotation operations.

5.4 Predominant Cause of Accidents/Incidents

A review of NTSB reportable accidents and incidents during autorotation training/instruction indicates that the predominant probable cause is failure to maintain main rotor revolutions per minute (rpm) (Nr) and airspeed within the Rotorcraft Flight Manual (RFM) or pilot’s operating handbook (POH) specified range, resulting in an excessive and unrecoverable rate of descent. Each helicopter has a recommended airspeed and rotor rpm for autorotations, specified in the RFM or POH. The RFM or POH must be consulted prior to flight in order to determine these performance considerations and comply with 14 CFR part 91, § 91.103.

6 AUTOROTATION TRAINING RECOMMENDATIONS

The following recommendations apply equally to both straight-in autorotations and the 180-degree turning autorotations. Instructors should teach the entry, descent (with and without turns), the go-around, and the flare recovery separately.

6.1 Initial Training

While the goal is for helicopter pilots to attain a safe level of proficiency in performing a 180-degree autorotation from 700 feet above ground level (AGL) (or from the pattern altitude, as appropriate), the FAA recommends that initial training for a 180-degree autorotation be introduced over a number of flight lessons and start with a much higher altitude as the entry point, progressively reducing the altitude and therefore gradually increasing the level of difficulty.

6.2 Higher Entry Point Autorotation

The instructor should first demonstrate a 180-degree autorotation with an entry from above 1,500 feet AGL using at least 1,000 feet to complete the turn but noting all the relevant points as described in paragraph 7 of this AC. This maneuver should be concluded by performing a power recovery and go-around no lower than 500 feet AGL.

6.3 Lower Entry Point Autorotation

Once the student is proficient in performing this maneuver to the go-around point at 500 feet, the instructor should then demonstrate the 180-degree autorotation from a lower entry point, such as 1,000 feet AGL. This maneuver should introduce the flare and power recovery to a suitable area on the ground. The student should then be given the opportunity to practice this maneuver with an entry at 1,000 feet AGL, terminating in a flare and power recovery at a safe hover altitude above the ground, until proficient from the lower altitude. The instructor can then select a lower entry altitude, such as 700 feet AGL (or the pattern altitude where the training is taking place) and demonstrate a further 180-degree autorotation to a flare and power recovery. The student should be taught, with careful monitoring from the instructor, to develop the necessary skills in executing an autorotation, bearing in mind that this maneuver has become more difficult for the student as altitude is reduced and time available for the 180-degree turn is now more limited.

6.4 The 300-Feet AGL Decision Check

The 300-feet AGL decision check is used to create a decision point at which the pilot, instructor, DPE, or ASI, based on specific parameters, makes a decision to either continue the autorotation or abort the maneuver and return to powered flight. It is important to impress upon the pilot the need to have the helicopter in a steady state at approximately 300 feet AGL in order to help ensure that a safe landing or power recovery can be accomplished. Prior to this decision point, all maneuvering is done to accomplish one thing; to place the helicopter in a position so that it can arrive at 100 feet above the ground with the proper rpm, airspeed, and attitude. Adjust flight controls to achieve the following parameters before approaching 300 feet AGL (instructors should be able to explain the parameters during the maneuver, not just before reaching 300 feet AGL):

Note: Instructors should not talk the student through corrective action, or try to manipulate the controls and attempt to correct the autorotation. If the conditions above are not met at the 300-feet AGL decision point, then immediately restore power and perform a go-around.

6.5 When and Where to Train

The selection of a location at which to perform a simulated engine failure during training should be made with the consideration that should the simulated engine failure turn into an actual emergency (experiencing an actual engine failure as the throttle is reduced to idle), the helicopter is in a position that a safe touchdown autorotation can be made to the landing area. Suitable areas that meet this criteria may be, but are not limited to, airports with hard surface runways or taxiways, designated hard surface off airport helicopter landing areas, large hard surface parking lots, large grass fields, and grass runways in good condition. If any doubt exists as to the condition of the surface, a ground or low reconnaissance should be conducted prior to conducting training.

7 TURNING AUTOROTATION TECHNIQUE

Turns (or a series of turns) can be made during autorotation to facilitate landing into the wind, avoiding obstacles, or reaching a suitable landing area. Turns during autorotation should be made early so that the remainder of the autorotation is flown identically to a straight-in autorotation. The technique below describes an autorotation with a 180-degree turn.

7.1 Technique for a 180-Degree Turning Autorotation to Touchdown

7.1.1 Establish the aircraft on a downwind heading at the recommended airspeed and parallel to the intended touchdown point. Taking the wind into account, establish the ground track at a distance laterally (that will allow a normal autorotative glide according to the RFM/POH) from the desired course line to the touchdown point. In strong crosswind conditions, be prepared to adjust the downwind leg closer or farther out, as appropriate. Use the autorotation entry airspeed recommended by the RFM or POH. When abeam the intended touchdown point, smoothly reduce collective, then reduce power to the engine to show a split between the rotor rpm and engine rpm. Apply appropriate antitorque pedal and cyclic to maintain proper attitude. Throughout the autorotation, pilots should continually cross-check aircraft attitude, rotor rpm, airspeed, and that the helicopter is in trim (centered trim ball).

7.1.2 After the descent and autorotation airspeed are established, initiate the 180-degree turn. For training operations, initially roll into a bank of at least 30 degrees, but no more than 50–60 degrees. It is important to maintain the proper airspeed, rotor rpm, and trim ball centered throughout the turn. Changes in the aircraft’s attitude and the angle of bank will cause a corresponding change in rotor rpm within normal limits. Do not allow the nose to pitch up or down excessively during the maneuver, as it may cause undesirable rotor rpm excursions. Pitot-static airspeed indications may be unreliable or lag during an autorotative turn. Pilots should also exercise caution to avoid using excessive aircraft pitch attitudes to chase airspeed indications in an autorotative turn.

Note: Approaching the 90-degree point, check the position of the landing area. The second 90 degrees of the turn should end with a rollout on a course line to the landing area. If the helicopter is too close, decrease the bank angle (to increase the radius of turn); if too far out, increase the bank angle (to decrease the radius of the turn). A bank angle of 50–60 degrees may be encountered during this turn. Rotor rpm control will require faster corrective measures to avoid rotor overspeeds in this scenario. Monitor the trim ball and adjust as necessary to maintain coordinated flight. Prior to passing through 300 feet AGL, if landing or making a surface-level power recovery, the turn should be completed and the helicopter aligned with the intended touchdown area. Upon reaching the course line, set the appropriate crosswind correction. If the collective pitch was increased to control the rpm, it may need to be lowered on rollout to prevent decay in rpm.

7.1.3 This maneuver should be immediately aborted at any point if the following criteria are not met: if the helicopter is not in a stabilized autorotative descent to landing profile (i.e., it is not aligned with the touchdown point after completing the 180-degree turn); if the rotor rpm is not within limits; if the helicopter is not at a proper attitude/airspeed; or if the helicopter is not under proper control at 300 feet. It is essential that the pilot on the controls (or an instructor, when intervening) immediately abort the maneuver and execute a smooth power recovery and go-around. It is important for the certificated flight instructor (CFI) who is intervening at this point to remember that the go-around is a far safer option than trying to recover lost rotor rpm and reestablish or recover to the hover, or even the preferred hover taxi.

7.2 Minimizing Altitude Loss

From all entry positions, but particularly true of the 180-degree entry, a primary concern is getting the aircraft into the course line with as much altitude remaining prior to touchdown as possible. Once the collective has been lowered and the engine set to parameters outlined in the RFM/POH for conducting practice autorotations, the helicopter will lose altitude. A delayed turn will result in a lower altitude when arriving on the course line. Additionally, an uncoordinated flight condition (trim ball not centered) will result in an increased rate of descent, which may become unrecoverable.

7.3 Interior and Exterior Scan Pattern

During the turn to the course line, pilots should use a scan pattern to see outside as well as inside the cockpit. Of primary importance outside is maintaining the appropriate descending attitude and a proper turn rate. Essential items to scan inside are rotor rpm and centered trim ball. Rotor rpm will build any time G-forces are applied to the rotor system. Usually this occurs in the turn to the course line and during the deceleration flare.

7.4 Maintaining Rotor RPM Range Throughout Maneuver

Rotor rpm should be maintained in the range recommended in the RFM or POH throughout the maneuver. Rotor rpm outside of the recommended range will result in a higher rate of descent and less glide-ratio. It is substantially harder to regain low-rotor rpm than it is to control high-rotor rpm. A combination of down collective, cyclic inputs, and maneuvering (as required) to increase the airflow through the rotor system may be required to regain rotor rpm. Sufficient altitude may not be available to perform these items, so extreme care must be taken to immediately react to decreasing rotor rpm. When the rotor rpm exceeds the desired value as a result of increased G-load in the turn, timely use of up collective will increase the pitch of the blades and slow the rotor to the desired rpm. In an autorotation, rotor rpm is the most critical element. It provides the lift required to stabilize an acceptable rate of descent and the energy necessary to cushion the landing. Collective should be moved to the full down position to maintain rotor rpm immediately following a loss of power. However, rapid or abrupt lowering of the collective could lead to inadvertent unusual attitudes, which may not be recoverable, depending on altitude.

7.5 Managing Energy

Energy is a very important property of all rotating components, and the kinetic energy stored in the rotor system is used to cushion the landing. More lift is produced at the bottom of an autorotation by raising the collective, which increases the angle of attack of the blades. The rotor rpm will also rapidly decay at this point, and it is essential to properly time the flare and the final collective pull to fully arrest the descent and cushion the landing. Upon arriving on the course line prior to the flare, the scan should focus almost entirely outside. The scan should include:

7.6 Autorotational Deceleration (Flare)

Every autorotational flare will be different depending on the existing wind conditions, airspeed, Density Altitude (DA), the specific make and model (M/M) of helicopter, and the aircraft gross weight.

7.7 Effects of Aborted Autorotation

Helicopters operating at a high DA will need to take into account the effects on the control of the helicopter when recovering from an aborted autorotation. Some effects to be considered are:

8 COMMON ERRORS

9 PILOT CURRENCY

To lower the likelihood of an accident, pilots who are not proficient in straight-in autorotations should not be expected to perform a 180-degree autorotation with an entry point below 1,000 feet AGL in a training environment without first practicing the maneuver from a higher entry point. If a pilot has not flown at all for a number of days (e.g., 10 days or more) or has not recently flown a 180-degree autorotation (e.g., within the last 30 days), flight instructors should reintroduce this maneuver. The pilot in training should start the training from a higher altitude and once again decrease the entry level altitude to minimize risk.

10 EXAMINER SUPERVISION

To mitigate the risk involved in this maneuver, DPEs or FAA ASIs should determine the applicant’s level of proficiency and recency of experience with autorotations (to include turning autorotations) during the oral portion of the practical test. This discussion should occur before the flight portion of the practical test, and should include a description of the number of autorotations that have been performed by the applicant from an entry point of 700 feet AGL or below.

11 PTS/AIRMAN CERTIFICATION STANDARDS (ACS) LISTING

This AC will be listed in the current editions of each PTS below as being associated with the straight-in and the 180-degree autorotation. This AC will be listed as a required reference document for the CFI practical test and will include a requirement for the CFI candidate to demonstrate a clear understanding of these recommendations during his or her examination by the DPE or ASI. When ACS for rotorcraft are published, this AC will be listed in those documents. Responses should indicate clear understanding of the various elements of energy management involved in the maneuver and the issues associated with the ability of low-time students to manage those energies.

12 WHERE YOU CAN FIND THIS AC

You can find this AC on the FAA’s Web site at http://www.faa.gov/regulations_policies/advisory_circulars. You can view FAA regulations at http://www.faa.gov/regulations_policies/faa_regulations/.

13 AC FEEDBACK FORM

For your convenience, the AC Feedback Form is the last page of this AC. Note any deficiencies found, clarifications needed, or suggested improvements regarding the contents of this AC on the Feedback Form.

John S. Duncan Director, Flight Standards Service

Advisory Circular Feedback Form

If you find an error in this AC, have recommendations for improving it, or have suggestions for new items/subjects to be added, you may let us know by contacting the General Aviation and Commercial Division (AFS-800) at 9-AFS-800-Correspondence@faa.gov, or the Flight Standards Directives Management Officer at 9 AWA-AFS-140-Directives@faa.gov.

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