Stall Recovery Template issued by FAA in June 2012.

Relevant extracts of FAA Advisory Circular 120 - 109 dated 08 Jun 2012, based on the Colgan Air, Air France and other stall related accidents at high and low altitudes.

TABLE 1. STALL RECOVERY TEMPLATE (WITH ASSOCIATED RATIONALE) 

1. Autopilot and autothrottle………………………………..Disconnect

Rationale: While maintaining the attitude of the airplane, disconnect the autopilot and autothrottle. Ensure the pitch attitude does not increase when disconnecting the autopilot. This may be very important in out-of-trim situations. Manual control is essential to recovery in all situations. Leaving the autopilot or autothrottle connected may result in inadvertent changes or adjustments that may not be easily recognized or appropriate, especially during high workload situations.

2. a) Nose down pitch control…........................................Apply until stall warning is eliminated
 b) Nose down pitch trim…….………………………..….As Needed 

Rationale: a) Reducing the angle of attack is crucial for recovery. This will also address autopilot-induced excessive nose up trim.
b) If the control column does not provide sufficient response, pitch trim may be necessary. However, excessive use of pitch trim may aggravate the condition, or may result in loss of control or high structural loads.

3. Bank…………………………………………………..…….Wings Level 

Rationale: This orients the lift vector for recovery.

4. Thrust …………………………………………….………….As Needed 

Rationale: During a stall recovery, maximum thrust is not always needed. A stall can occur at high thrust or at idle thrust. Therefore, the thrust is to be adjusted accordingly during the recovery. For airplanes with engines installed below the wing, applying maximum thrust may create a strong nose-up pitching moment if airspeed is low. For airplanes with engines mounted above the wings, thrust application creates a helpful pitch-down tendency. For propeller-driven airplanes, thrust application increases the airflow around the wing, assisting in stall recovery.

5. Speed brakes/Spoilers……….…….…………………………..Retract 

Rationale: This will improve lift and stall margin.

6. Return to the desired flightpath.

Rationale: Apply gentle action for recovery to avoid secondary stalls then return to desired flightpath.

FINE AIR DC-8 ACCIDENT AT MIAMI 07 AUG 1997

(From Flight Safety Foundation website and NTSB accident Report)

Executive Summary

Fine Air Flight 101 was originally scheduled to depart Miami for Santo Domingo at 09:15 using another DC-8 airplane, N30UA, to carry cargo for Aeromar. Due to a delay of the inbound aircraft, Fine Air substituted N27UA for N30UA and rescheduled the departure for 12:00. N27UA arrived at Miami at 09:31 from San Juan, Puerto Rico, and was parked at the Fine Air hangar ramp. The security guard was not aware of the airplane change, and he instructed Aeromar loaders to load the airplane in accordance with the weight distribution form he possessed for N30UA. The first cargo pallet for flight 101 was loaded onto N27UA at 10:30 and the last pallet was loaded at 12:06. The resulting center of gravity (CG) of the accident airplane was near or even aft of the airplane’s aft CG limit. After the three crew members and the security guard had boarded the plane, the cabin door `was closed at 12:22. 

Eleven minutes later the flight obtained taxi clearance for runway 27R. The Miami tower controller cleared flight 101 for takeoff at 12:34. Takeoff power was selected and the DC-8 moved down the runway. The flight crew performed an elevator check at 80 knots. Fourteen seconds later the sound of a thump was heard. Just after calling V1 a second thump was heard. Two seconds later the airplane rotated. Immediately after takeoff the airplane pitched nose-up and entered a stall. The DC-8 recovered briefly from the stall, and stalled again. The airplane impacted terrain in a tail first, right wing down attitude. it slid west across a road (72nd Avenue) and into the International Airport Center at 28th Street and burst into flames. Investigation showed that the center of gravity resulted in the airplane’s trim being mis-set by at least 1.5 units airplane nose up, which presented the flight crew with a pitch control problem on takeoff.

FINDINGS (Findings that are relevant to pilots are being reproduced here from the NTSB accident report, which can be accessed at http://www.ntsb.gov/doclib/reports/1998/AAR9802.pdf):

• The center of gravity (CG) of the accident airplane was near or even aft of the airplane’s aft CG limit.
• The center of gravity shift resulted in the airplane’s trim being mis-set by at least 1.5 units airplane nose up (2.4 minus 0.9 units at 94,119 pounds).
• The aft center of gravity (CG) location and mis-trimmed stabilizer presented the flight crew with a pitch control problem; however, because the actual CG location could not be determined, the severity of the control problem could not be determined.
• The mistrim of the airplane (based on the incorrectly loaded cargo) presented the flightcrew with a situation that, without prior training or experience, required exceptional skills and reactions that cannot be expected of a typical line pilot.

PROBABLE CAUSE: "The National Transportation Safety Board determines that the probable cause of the accident, which resulted from the airplane being mis-loaded to produce a more aft center of gravity and a correspondingly incorrect stabilizer trim setting that precipitated an extreme pitch-up at rotation, was (1) the failure of Fine Air to exercise operational control over the cargo loading process; and (2) the failure of Aeromar to load the airplane as specified by Fine Air. Contributing to the accident was the failure of the FAA to adequately monitor Fine Airs operational control responsibilities for cargo loading and the failure of the FAA to ensure that known cargo-related deficiencies were corrected at Fine Air."

ALLIANCE AIR ACCIDENT AT PATNA: 17 JUL 2000

(From DGCA Accident Summary for year 2000)

Brief Description:            Boeing 737 aircraft VT-EGD, owned by Indian Airlines Ltd. and operated by Airlines Allied Services Ltd. took off from NSCBI Airport Kolkata at 0615 hrs on 17.07.2000 for Patna – Lucknow - Delhi. There were 58 persons on board, including six crewmembers. At approx 0713 hrs, the aircraft informed Patna ATC of the estimated arrival time at Patna as 0736 hrs. The aircraft informed Patna ATC at 0732 hrs that it would like to do a 360-degree due to being high on approach. The ATC informed the aircraft to report final for R/W 25 after carrying out a 360-degree turn and the pilot acknowledged the same. This was the last communication recorded between the aircraft and the ATC. During the approach for R/W 25 at Patna, the aircraft turned steeply to the left, losing height, and collided with the tree in the approach funnel and crashed in the Gardani Bagh area near Patna Airport. The aircraft was totally destroyed due impact with the ground and post impact fire.

The probable cause of the accident:       The cause of the accident was loss of control of the aircraft due Human Error (Aircrew). The crew had not followed the correct approach procedure, which resulted in the aircraft being high on approach. They kept the engines at idle thrust and allowed the air speed to reduce to a lower than normally permissible value on approach. They then maneuvered the aircraft with high pitch attitude and executed rapid roll reversals. This resulted in actuation of the stick shaker stall warning indicating an approaching stall. At this stage, the crew initiated a Go Around procedure instead of approach to Stall Recovery procedure resulting in an actual stall of the aircraft, loss of control and subsequent impact with the ground.

Factor: Pilot:      Non-adherence to standard operating procedure.

BASICS OF AN AERODYNAMIC STALL

This is written from a pilot’s point of view with the aim of giving a theoretical aerodynamic background to the actions that one takes in the cockpit. These actions would become instinctive if one understands the basic theory. We are not designers or engineers, but we need to fly the aircraft safely from A to B, under all conditions. Under normal conditions we would never be operating close to stall. The highest AsOA that we encounter in flight are during the take-off and landing phases.  However, when operating under conditions that are not normal we are still required to fly that aircraft safely and thus we need to understand how our aircraft behaves at all times.

• ·         In flight we have four forces that we should be aware of at all times. To maintain steady straight and level flight the Lift has to balance weight and the thrust has to balance the drag, and the sum of the moments has to be zero. This also implies that the Power available is equal to the power required. If the Power available is more than the Power required then the aircraft would have a ROC, and vice versa. Power required = Drag X TAS. Power available is Thrust X TAS.
• ·         A stall is a condition of flight in which the aircraft has exceeded the stalling angle of attack or the critical angle leading to a sharp decrease in co-efficient of lift and a sharp increase in the co-efficient of drag. (Please refer to the AOA vs Cl/ Cd graphs).
• ·         The decrease in Cl leads to loss of lift as L = Cl ½ pv2S. In straight and level flight the lift is now no longer able to balance the weight.
• ·         The increase in co-efficient of drag increases the drag leading to a power deficit, as the power available at the same throttle settings is now less than the power required. On a training aircraft with rectangular wings, propeller slipstream and high thrust line, the wing stalls and the nose pitches down, helping in recovery of the aircraft from the stalled condition.
• ·         This situation changes in aircraft that fly at high altitude, high speed, have sweep back wings and a thrust line below the CG (due to low slung engines). Sweep back wings tend to stall at the tips first causing the nose to pitch up; any addition of thrust from the low slung engines would aggravate the pitch up situation and lead to a stall.
• ·         In a power deficit situation, the aircraft will develop a descent. When the aircraft commences descent, the direction of the relative airflow changes, as the flight path of the aircraft has changed.  The relative airflow comes from further below than earlier leading to an increase in AOA – reducing Cl further and increasing Cd further. We are now entering into a deep stall zone which is more pronounced on sweep back and delta wings. The positioning of the tail also has an effect.  Any other phenomenon like icing could also lead to reduction of Cl and increase in Cd.
• ·         The only way out is to unstall the aircraft by reducing the AOA by aligning the aircraft with the relative airflow coming from below OR in pilot’s parlance by pushing forward on the control column. The throttle is advanced to increase the thrust so that the power available increases to match the power required.
• ·         Once the aircraft unstalls, the aircraft can be eased out. This procedure has to be followed on all aeroplanes – the basic theoretical considerations do not change very much and you can understand the reason why ; the manufacturers give the finer points which would be peculiar to that aircraft type.
• ·         The basic fact is that whether one flies the C-152 or the A-380, the aircraft needs to be supported by the air in which it flies.
• ·         The airflow going around the aerofoil is what generates the lift and the aerofoil (and in turn the wing too) stalls when the airflow ‘separates’ from the aerofoil at a forward position on the chord, leading to sharp loss of lift. (As the AOA increases, the separation point keeps moving forward.)
• ·         Every aerofoil has different aerodynamic characteristics, as can be seen in the books. When icing takes place the aerofoil shape changes, and so do its aerodynamic characteristics – Cl, Cd and separation of airflow too. It would happen every time the aerofoil shape changes – it could be because of dirt, pigeon shit on the wing or any other phenomenon.
• ·         Standard operating Procedures are laid down for all normal operations that a company undertakes, and are a pilot’s life line and should be followed meticulously to go from A to B safely under all conditions – normal or not normal.

SPANAIR CRASH ON 20 AUG 2008

(Courtesy: The internet)

Brief Description

A MD-82 aircraft operated by Spanair from Madrid-Barajas (MAD) to Gran Canaria (LPA) was destroyed when it crashed on take-off at MAD, killing 154 occupants, including all six crew members, and seriously injuring 18. The estimated departure time of the flight was 13:00. The aircraft was authorized to start-up at 13:06:15. It taxied to runway 36L. The flaps were extended to 11° for take-off. The aircraft was cleared for takeoff at 13:24:57. The crew informed the ATC at 13:26:27 that they had a problem and that they had to exit the runway. At 13:33:12, they communicated that they were returning to the stand.

The crew had detected an overheating Ram Air Temperature (RAT) probe. The aircraft returned to the apron. The maintenance confirmed the malfunction described, checked the RAT probe heating section of the Minimum Equipment List (MEL) and opened the electrical circuit breaker that connected the heating element. Once complete, it was proposed and accepted that the aircraft be dispatched. The aircraft was topped off with 1080 liters of kerosene and at 14:08:01 it was cleared for engine start-up and to taxi to runway 36L for takeoff.

The crew continued with the tasks to prepare the airplane for the flight. The conversations on the cockpit voice recorder revealed certain expressions corresponding to the before engine start checklists, the normal start list, the after start checklist and the taxi checklist. On the final taxi segment the crew concluded its checks with the takeoff imminent checklist. At 14:23:14, the aircraft was cleared for take-off from runway 36L. Along with the clearance, the control tower informed the aircraft that the wind was from 210° at 5 knots.

At 14:23:19, the crew released the brakes for takeoff. Engine power had been increased a few seconds earlier and at 14:23:28 its value was 1.4 EPR. Power continued to increase to a maximum value of 1.95 EPR during the aircraft’s ground run. The CVR recording shows the crew calling out "V1" at 14:24:06, at which time the DFDR recorded a value of 147 knots for calibrated airspeed (CAS), and "rotate" at 14:24:08, at a recorded CAS of 154 knots. The DFDR recorded the signal change from ground mode to air mode from the nose gear strut ground sensor. The stall warning stick shaker was activated at 14:24:14 and on three occasions the stall horn and synthetic voice sounded in the cockpit: "[horn] stall, [horn] stall, [horn] stall". Impact with the ground took place at 14:24:23.

During the entire takeoff run until the end of the CVR recording, no noises were recorded involving the takeoff warning system (TOWS) advising of an inadequate takeoff configuration. During the entire period from engine start-up while at parking stand R11 to the end of the DFDR recording, the values for the two flap position sensors situated on the wings were 0°.
The length of the takeoff run was approximately 1950 m. Once airborne, the aircraft rose to an altitude of 40 feet above the ground before it descended and impacted the ground. During its trajectory in the air, the aircraft took on a slight left roll attitude. The crew momentarily retarded the engine throttles, increased the pitch angle and did not correct for the left roll angle. The left roll was followed by a fast 20° roll to the right, another slight roll to the left and another abrupt roll to the right of 32°. The maximum pitch angle recorded during this process was 18°.

The aircraft’s tailcone was the first part to impact the ground, almost simultaneously with the right wing tip and the right engine cowlings. The marks from these impacts were found on the right side of the runway strip as seen from the direction of the takeoff, at a distance of 60 m, measured perpendicular to the runway centerline, and 3207.5 m away from the threshold, measured in the direction of the runway. The aircraft then traveled across the ground an additional 448 m until it reached the side of the runway strip, tracing out an almost linear path at a 16° angle with the runway. It lost contact with the ground after reaching an embankment/drop-off beyond the strip, with the marks resuming 150 m away, on the airport perimeter road, whose elevation is 5.50 m lower than the runway strip. The aircraft continued moving along this irregular terrain until it reached the bed of the Vega stream, by which point the main structure was already in an advanced state of disintegration. It is here that it caught on fire. The distance from the initial impact site on the ground to the farthest point where the wreckage was found was 1093m.