The MD-80 with is swept back dihedral wing and T-tail, exhibits a considerable amount of dihedral effect (roll due to yawl. The effect is especially noticeable at moderately high angles of attack such as during heavy-weight takeoffs with speeds between V2 and V2 + 10 knots. Consequently, the rudder is the primary control for maintaining a wingslevel attitude. The wings-level, ball-centered technique provides the best compromise between climb performance and flying qualities.

The pilot should minimize use of ailerons during on engine failure on takeoff and should try to keep the wheel centered. Any aileron deflection post the 5 degree wheel angle extends the spoilers, thereby increasing aircraft drag, an undesirable condition with an engine failure. Any sustained aileron deflection required to maintain level wings indicates an incorrect amount of rudder.

The single-engine characteristics of the MD-80 are excellent at oil gross weights, although the characteristics are not identical. While engine failure at high gross weight results in minimal aircraft climb performance, high gross weight takeoffs are not necessarily the most challenging. This is because flying qualities, or the ability to control pitch, bank and yaw, are better at the high V2 speeds of high gross weight aircraft. Because a lightweight aircraft has a relatively low V2 speed, the effectiveness of the rudder to counteract the yaw generated by the remaining good engine is reduced. Rudder effectiveness is directly proportional to the indicated airspeed and airflow over the foil.

To summarize even though performance of the aircraft is best at tow gross weights, flying qualities are best at high gross weights when operating with only one engine at or near V2·

ENGINE AND AIRCRAFT SYSTEMS DESIGNED TO AUGMENT THRUST. Two separate systems, the automatic reserve thrust (ART) system and the automatic thrust restoration (ATR) system, attempt to provide maximum available thrust when the performance of one engine significantly differs from the other during takeoff.

AUTOMATIC RESERVE THRUST SYSTEM. The ART system automatically detects an engine failure and subsequently increases the thrust of the operating engine during takeoff. ART is "read)/' on the ground when the aircraft has weight on wheels for at least 20 seconds, the ART switch is in the AUTO position, engines are operating near idle, slats are extended and ART self test is completed. The system is subsequently "armed" when both engines are spooled up to at (east 64 percent N1.

ART actuates when the' digital flight guidance computer (DFGC) detects any one of the following:
· 30,2 percent differential in N1
· Invalid N1.
· DFGC failure.
· Electrical power loss.
· Manual DFGC switching.

Upon actuation, ART increases the engine pressure ratio (EPR) of the operating engine(s) from normal takeoff to maximum takeoff by operating the solenoid operated fuel valve in the engine fuel control. This is on increase of approximately 0,05 EPR Once ART is actuated, the maximum takeoff EPR is displayed on the thrust rating indicator and the EPR gauge and the system fuel valve remains open until the ART switch is placed in the OFF position. ART operation is independent of the autothrottle.

If ART fails its self test, the ART INOP annunciation illuminates. Although dispatch is allowed with a failed self test, the ART switch must be placed in the OFF position to disable the ART system.

AUTOMATIC THRUST RESTORATION SYSTEM. The ATR feature of the DFGC increases thrust under certain conditions during an engine failure on takeoff. This feature is specifically valuable during thrust cutbacks for noise abatement. If a thrust cutback is made and an engine subsequently fails, the ATR restores maximum takeoff thrust on good engine. Once activated, the ATR unclamps the throttles, if the autothrottle system is engaged and moves both throttles equally until one of the engines reaches the go-around EPR limit.

The ATR is armed if the flight director pitch axis is in takeoff mode, the aircraft is above 350 feet radio altitude and both engine EPRs are below the go-around EPR limit. After arming, the system activates if the differences between the engines are greater than or equal to 0,25 EPR and 7 percent N1 in the same direction or, for DFGC models -930/-970/-971 and later, aircraft vertical speed decreases to level flight or less for 5 seconds. In these cases the throttles unclamp if the autothrottle system is engaged and move to the go-around EPR limit.

If ART is armed and the ATR is activated, the EPR limit is the maximum in flight takeoff rating less the amount of thrust that ART is designed to provide. This reduction prevents overboosting the engine if ART subsequently actuates. The autothrottle system must be ON for the ATR to advance the throttles.

FLIGHT DIRECTOR. When the DFGC recognizes an engine failure it provides valid pitch commands to the flight director. The FD then commands the pitch attitude required to achieve the preferred engine-out climb speed. If an engine fails prior to V2 the flight director commands a pitch attitude to capture and maintain V2· If an engine fails at a speed between V2 and V2 + 10 knots, the FD maintains that speed. If an engine fails at a speed above V2 + 10 knots, the FD commands a pitch attitude to capture and maintain V2 + 10 knots. The DFGC uses the same engine failure detection logic used by the ATR system.

RECOMMENDED TECHNIQUES. Engine fire, engine failure/seizure/separation, and engine surge/stall are events that can bring ART, ATR and the FD into action. However, each malfunction has different considerations.

ENGINE FIRE. The primary danger of an engine fire on takeoff is an imminent loss of thrust. The danger from fire itself is minimal due to substantial fireproofing. The engine pylons contain a firewall to isolated fire from the fuselage. In addition, multiple fireseals further protect the engine nacelles and aircraft fuselage.

An aircraft experiencing on engine fire during takeoff should be flown as though the engine has failed. Although the fire bell may be silenced without delay, thrust should not be retarded below 400 feet above ground level (AGL). After passing 400 feet AGL, pilot discretion determines when to retard the throttle and accomplish engine fire emergency procedures.

ENGINE FAILURE, SEIZURE AND SEPARATION. Engine failures, seizures and separations cause the immediate and total loss of thrust, which degrades both climb performance and flying qualities.

The key to flying a good takeoff and climb-out profile with a failed, seized or separated engine is to supply adequate rudder to counteract the asymmetric thrust created by an engine out condition. Of secondary importance is maintaining proper airspeed through pitch.

Proper airspeed is important because the engine out climb gradient mandated by the FAA - a 2,4 percent climb gradient between 35 and 400 feet - is based upon the prescribed FD commanded airspeed defined previously. The actual climb gradient is reduced for speeds significantly above or below that level. Furthermore, for speeds below that commanded by the FD, the dihedral effect is worsened due to the aircraft's higher angle of attack. This results in a significantly higher rudder requirement, thereby making bank and roll rate control more difficult.
ENGINE STALLS AND SURGES. If an engine surges on takeoff, aural thumps and bangs may be heard in the cockpit. However, because of the long MD-80 fuselage and short separation between the engines, it is difficult to use sound to determine which engine is surging. The best technique is to analyze the engine instruments. The most prominent indication of an engine surge or stall is erratic or unstable N1 or EPR or simultaneously decreasing EPR and increasing exhaust gas temperature. Other engine parameters may also provide some additional clues.

A surging or stalling engine usually does not activate ART, but the condition does usually activate ATR, thereby unclamping the throttles and moving them to the go-around setting.

If an engine stalls or surges on takeoff, the pilot should fly the aircraft under the assumption that engine failure is imminent. The engine-out profile should be flown, leveling off at the acceleration altitude. In addition, immediate steps must be taken to reduce the strain on the affected engine in an attempt to remove-the surging condition. Recent FAA directives require the pilot to disconnect the autothrottle when encountering engine stalls/surges on takeoff. The pilot should simultaneously reduce the throttle of the affected engine, to idle if necessary, to clear the surge. Most surges and stalls recover when this is done. If the surging engine cannot be identified, consider retarding both throttles if obstacle clearance permits.

COLD WEATHER OPERATIONS. Engine stalls and surges are more likely to occur during cold weather operations. A major cause of engine stalls and surges is ice-induced foreign object damage. To minimize problems, Douglas recommends adhering to MD-80 Flight Crew Operating Manual procedures. Pilots should perform the following functions:
· Properly de-ice the aircraft before takeoff.
· Turn engine ignition ON before selecting engine anti-ice.
· Turn engine anti-ice ON when icing conditions exist, such as when the outside air temperature is below 6º C and visible moisture is present or the temperature/dew point spread is 3º C.
· Run up the engines, with the engine anti-ice system ON, to 70 percent N1, for a minimum of 15 seconds once every 10 minutes prior to takeoff when the above climatic conditions exist.

CONCLUSION. Even though the MD-80 flies well on one engine, even during takeoff, the best way to handle the condition is by using a knowledge of pertinent engine and aircraft systems to plan ahead.