Ground Movement and Engine Operation

1-14 Immediately after the engine starts, check the oil pressure indicator. If oil pressure does not show within 30 seconds, stop the engine and determine the trouble. If oil pressure is indicated, adjust the throttle to the aircraft manufacturer’s specified rpm for engine warm up. Warm up rpm is usually between 1,000 to 1,300 rpm. Most aircraft reciprocating engines are air cooled and depend on the forward speed of the aircraft to maintain proper cooling. Therefore, particular care is necessary when operating these engines on the ground. During all ground running, operate the engine with the propeller in full low pitch and headed into the wind with the cowling installed to provide the best degree of engine cooling. Closely monitor the engine instruments at all times. Do not close the cowl flaps for engine warm-up, they need to be in the open position while operating on the ground. When warming up the engine, ensure that personnel, ground equipment that may be damaged, or other aircraft are not in the propeller wash.

Extinguishing Engine Fires In all cases, a fireguard should stand by with a CO 2 fire extinguisher while the aircraft engine is being started. This is a necessary precaution against fire during the starting procedure. The fireguard must be familiar with the induction system of the engine so that in case of fire, they can direct the CO2 into the air intake of the engine to extinguish it. A fire could also occur in the exhaust system of the engine from liquid fuel being ignited in the cylinder and expelled during the normal rotation of the engine. If an engine fire develops during the starting procedure, the operator should continue cranking to start the engine and extinguish the fire. If the engine does not start and the fire continues to burn, discontinue the start attempt. The fireguard then extinguishes the fire using the available equipment. The fireguard must observe all safety practices at all times while standing by during the starting procedure.

Turboprop Engines

The starting of any turbine engine consists of three steps that must be carried out in the correct sequence. The starter turns the main compressor to provide airflow though the engine. At the correct speed that provides enough airflow, the igniters are turned on and provide a hot spark to light the fuel that is engaged next. As the engine accelerates, it reaches a self- sustaining speed and the starter is disengaged. The various covers protecting the aircraft must be removed. Carefully inspect the engine exhaust areas for the presence of fuel or oil. Make a close visual inspection of all accessible parts of the engines and engine controls, followed by an inspection of all nacelle areas to determine that all inspection and access plates are secured. Check sumps for water. Inspect air inlet areas for general condition and foreign material.

Check the compressor for free rotation, when the installation permits, by reaching in and turning the blades by hand. The following procedures are typical of those used to start turboprop engines. There are, however, wide variations in the procedures applicable to the many turboprop engines. Therefore, do not attempt to use these procedures in the actual starting of a turboprop engine. These procedures are presented only as a general guide for familiarization with typical procedures and methods. For starting of all turboprop engines, refer to the detailed procedures contained in the applicable manufacturer’s instructions or their approved equivalent.

Turboprop engines are usually fixed turbine or free turbine. The propeller is connected to the engine directly in a fixed turbine, resulting in the propeller being turned as the engine starts. This provides extra drag that must be overcome during starting. If the propeller is not at the “start” position, difficulty may be encountered in making a start due to high loads. The propeller is in flat pitch at shut down and subsequently in flat pitch during start because of this. The free turbine engine has no mechanical connection between the gas generator and the power turbine that is connected to the propeller. In this type of engine, the propeller remains in the feather position during starting and only turns as the gas generator accelerates.

Instrumentation for turbine engines varies according to the type of turbine engine. Turboprop engines use the normal instruments—oil pressure, oil temperature, inter-turbine temperature (ITT), and fuel flow. They also use instruments to measure gas generator speed, propeller speed, and torque produced by the propeller. [Figure 1-15] A typical turboprop uses a set of engine controls, such as power levelers (throttle), propeller levers, and condition levers. [Figure 1-16] The first step in starting a turbine engine is to provide an adequate source of power for the starter. On smaller turbine engines, the starter is an electric motor that turns the engine through electrical power. Larger engines need a much more powerful starter. Electric motors would be limited by current flow and weight. Air turbine starters were developed that were lighter and produced sufficient power to turn the engine at the correct speed for starting. When an air turbine starter is used, the starting air supply may be obtained from an APU onboard the aircraft, an external source (ground air cart), or an engine cross-bleed operation. In some limited cases, a low-pressure, large-volume tank can provide the air for starting an engine. Many smaller turboprop engines are started using the starter/generator, that is both the engine 1-15 starter and the generator.

While starting an engine, always observe the following: • Always observe the starter duty cycle. Otherwise, the starter can overheat and be damaged. • Assure that there is enough air pressure or electrical capacity before attempting a start. • Do not perform a ground start if turbine inlet temperature (residual temperature) is above that specified by the manufacturer. • Provide fuel under low pressure to the engine’s fuel pump. Turboprop Starting Procedures To start an engine on the ground, perform the following operations: 1. Turn the aircraft boost pumps on. 2. Make sure that the power lever is in the “start” position.

3. Place the start switch in the “start” position. This starts the engine turning. 4. Place the ignition switch on. (On some engines, the ignition is activated by moving the fuel lever.) 5. The fuel is now turned on. This is accomplished by moving the condition lever to the “on” position. 6. Monitor the engine lights of the exhaust temperature. If it exceeds the limits, shut the engine down. 7. Check the oil pressure and temperature. 8. After the engine reaches a self-sustaining speed, the starter is disengaged. 9. The engine continues to accelerate up to idle. 10. Maintain the power lever at the “start” position until the specified minimum oil temperature is reached.

11. Disconnect the ground power supply, if used. If any of the following conditions occur during the starting sequence, turn off the fuel and ignition switch, discontinue the start immediately, make an investigation, and record the findings. • Turbine inlet temperature exceeds the specified maximum. Record the observed peak temperature. • Acceleration time from start of propeller rotation to stabilized rpm exceeds the specified time. • There is no oil pressure indication at 5,000 rpm for either the reduction gear or the power unit. • Torching (visible burning in the exhaust nozzle). • The engine fails to ignite by 4,500 rpm or maximum motoring rpm.

• Abnormal vibration is noted or compressor surge occurs (indicated by backfiring). • Fire warning bell rings. (This may be due to either an engine fire or overheat.) Turbofan Engines Unlike reciprocating engine aircraft, the turbine-powered aircraft does not require a preflight run-up unless it is necessary to investigate a suspected malfunction. Before starting, all protective covers and air inlet duct covers are removed. If possible, head the aircraft into the wind to obtain better cooling, faster starting, and smoother engine performance. It is especially important that the aircraft be headed into the wind if the engine is to be trimmed.

The run-up area around the aircraft is cleared of both personnel and loose equipment. The turbofan engine intake and exhaust hazard areas are illustrated in Figure 1-17 . Exercise care to ensure that the run-up area is clear of all items, such as nuts, bolts, rocks, shop towels, or other loose debris. Many very serious accidents have occurred involving personnel in the vicinity of turbine engine air inlets. Use extreme caution when starting turbine aircraft. Check the aircraft fuel sumps for water or ice. Inspect the engine air inlet for general condition and the presence of foreign objects. Visually inspect the fan blades, forward compressor blades, and the compressor inlet guide vanes for nicks and other damage. If possible, check the fan blades for free rotation by turning the fan blades by hand. All engine controls must be operational. Check engine instruments and warning lights for proper operation.

Starting a Turbofan Engine The following procedures are typical of those used to start many turbine engines. There are, however, wide variations in the starting procedures used for turbine engines, and no attempts are to be made to use these procedures in the actual starting of an engine. These procedures are presented only as a general guide for familiarization with typical procedures and methods. In the starting of all turbine engines, refer to the detailed procedures contained in the applicable manufacturer’s instructions or their approved equivalent. Most turbofan engines can be started by either air turbine or electrical starters. Air-turbine starters use compressed air from an external source as discussed earlier. Fuel is turned on either by moving the start lever to “idle/start” position or by opening a fuel shutoff valve. If an air turbine starter is used, 1-16 FUEL FLOW RPH X 100 0 12 6 3 4 5 °C PSI OIL 0 50 100 150 200 20 -200 60 100 140 °C PSI OIL 0 50 100 150 200 20 -200 60 100 140 FUEL FLOW RPH X 100 0 12 6 3 4 5 TORQUE FTLB X 100 0 2 4 6 810121416 18 20 22 24 26 TORQUE FTLB X 100 0 2 4 6 810121416 18 20 22 24 26 PROP RPH X 100 0 5 10 13 14 15161718 19 20 21 22 23 PROP RPH X 100 0 5 10 13 14 15161718 19 20 21 22 23 F E A T H E R P R O P E L E R I D L E R E V E R S E P O W E R S T O P RUN GA Power levers Condition levers Prop levers the engine “lights off” within a predetermined time after the fuel is turned on. This time interval, if exceeded, indicates a malfunction has occurred and the start must be discontinued.

Most turbofan engine controls consist of a power lever, reversing levers, and start levers. Newer aircraft have replaced the start levers with a fuel switch. [Figure 1-18] Turbofan engines also use all the normal instruments speeds, (percent of total rpm) exhaust gas temperature, fuel flow, oil pressure, and temperature. An instrument that measures the amount of thrust being delivered is the engine pressure ratio. This measures the ratio between the inlet pressures to the outlet pressure of the turbine. The following procedures are useful only as a general guide and are included to show the sequence of events in starting a turbofan engine.

1. If the engine is so equipped, place the power lever in the “idle” position. 2. Turn the fuel boost pump(s) switch on. 3. A fuel inlet pressure indicator reading ensures fuel is being delivered to engine fuel pump inlet. 4. Turn engine starter switch on. Note that the engine rotates to a preset limit. Check for oil pressure. 5. Turn ignition switch on. (This is usually accomplished by moving the start lever toward the “on” position. A micro switch connected to the leveler turns on the ignition.) 6. Move the start lever to “idle” or “start” position, this starts fuel flow into the engine. 7. Engine start (light off) is indicated by a rise in exhaust gas temperature.

8. If a two-spool engine, check rotation of fan or N1. 9. Check for proper oil pressure. 10. Turn engine starter switch off at proper speeds. 11. After engine stabilizes at idle, ensure that none of the engine limits are exceeded. 12. Newer aircraft drop off the starter automatically. Auxiliary Power Units (APUs) APUs are generally smaller turbine engines that provide compressed air for starting engines, cabin heating and cooling, and electrical power while on the ground. Their operation is normally simple. By turning a switch on and up to the start position (spring loaded to on position), the engine starts automatically. During start, the exhaust gas temperature must be monitored. APUs are at idle at 100 percent rpm with no load. After the engine reaches its operating rpm, it can be used for cooling or heating the 1-17 cabin and for electrical power. It is normally used to start the main engines.

Unsatisfactory Turbine Engine Starts Hot Start A hot start occurs when the engine starts, but the exhaust gas temperature exceeds specified limits. This is usually caused by an excessively rich air-fuel mixture entering the combustion chamber. This condition can be caused by either too much fuel or not enough airflow. The fuel to the engine must be shut off immediately. False or Hung Start False or hung starts occur when the engine starts normally, but the rpm remains at some low value rather than increasing to the normal starting rpm. This is often the result of insufficient power to the starter or the starter cutting off before the engine starts self-accelerating. In this case, shut the engine down.

Engine Fails to Start The engine failing to start within the prescribed time limit can be caused by lack of fuel to the engine, insufficient or no electrical power to the exciter in the ignition system, or incorrect fuel mixture. If the engine fails to start within the prescribed time, shut it down. In all cases of unsatisfactory starts, the fuel and ignition must be turned off. Continue rotating the compressor for approximately 15 seconds to remove accumulated fuel from the engine. If unable to motor (rotate) the engine, allow a 30-second fuel draining period before attempting another start.

Towing of Aircraft

Movement of large aircraft about the airport, flight line, and hangar is usually accomplished by towing with a tow tractor (sometimes called a “tug”). [Figure 1-19] In the case of small aircraft, some moving is accomplished by hand pushing on the correct areas of the aircraft. Aircraft may also be taxied about the flight line but usually only by certain qualified personnel. Towing aircraft can be a hazardous operation, causing damage to the aircraft and injury to personnel, if done recklessly or carelessly. The following paragraphs outline the general procedure for towing aircraft. However, specific instructions for each model of aircraft are detailed in the manufacturer’s maintenance instructions and are to be followed in all instances.

Before the aircraft to be towed is moved, a qualified person must be in the flight deck to operate the brakes in case the tow bar fails or becomes unhooked. The aircraft can then be stopped, preventing possible damage. Some types of tow bars available for general use can be used for many types of towing operations. [Figure 1-20] These bars are designed with sufficient tensile strength to pull most aircraft, but are not intended to be subjected to torsional or twisting loads. Many have small wheels that permit them to be drawn behind the towing vehicle going to or from an aircraft. When the bar is attached to the aircraft, inspect all the engaging devices for damage or malfunction before moving the aircraft.

Additionally, some aircraft have tow steering turn limits. Some tow bars are designed for towing various types of aircraft. However, other special types can be used on a particular aircraft only. Such bars are usually designed and built by the aircraft manufacturer. When towing the aircraft, the towing vehicle speed must be reasonable, and all persons involved in the operation must be alert. When the aircraft is stopped, do not rely upon the brakes of the towing vehicle alone to stop the aircraft. The person in the flight deck must coordinate the use of the aircraft brakes with those of the towing vehicle. A typical smaller aircraft tow tractor (or tug) is shown in Figure 1-21.

The attachment of the tow bar varies on different types of aircraft. Aircraft equipped with tail wheels are generally towed forward by attaching the tow bar to the main landing gear. In most cases, it is permissible to tow the aircraft in reverse by attaching the tow bar to the tail wheel axle. Any time an aircraft equipped with a tail wheel is towed, the tail wheel must be unlocked or the tail wheel locking mechanism may damage or break. Aircraft equipped with tricycle landing gear are generally towed forward by attaching a tow bar to the axle of the nosewheel. They may also be towed forward or backward by attaching a towing bridle or specially designed towing bar to the towing lugs on the main landing gear. When an aircraft is towed in this manner, a steering bar is attached to the nosewheel to steer the aircraft.

The following towing and parking procedures are typical of one type of operation. They are examples and not necessarily suited to every type of operation. Aircraft ground-handling personnel must be thoroughly familiar with all procedures pertaining to the types of aircraft being towed and local operation standards governing ground handling of aircraft. Competent persons that have been properly checked out direct the aircraft towing team. 1. The towing vehicle driver is responsible for operating the vehicle in a safe manner and obeying emergency stop instructions given by any team member. 2. The person in charge assigns team personnel as wing walkers. A wing walker is stationed at each wingtip, in such a position that they can ensure adequate clearance 1-18 Distance in feet Velocity in knots = K Temperature in °F 125° 60 K 700° 900 K 500° 500 K 300° 300 K 200° 200 K 150° 100 K 125° 40 K 150° 60 K 200° 100 K 300° 200 K 200 150 100 50 0 100º 35 K 30 feet 25 feet 100° 12 feet 25 K 25 feet Exhaust Air intake idle Air intake takeoff 1-19 of any obstruction in the path of the aircraft. A tail walker is assigned when sharp turns are to be made or when the aircraft is to be backed into position.

3. A qualified person occupies the pilot’s seat of the towed aircraft to observe and operate the brakes as required. When necessary, another qualified person is stationed to watch and maintain aircraft hydraulic system pressure. 4. The person in charge of the towing operation verifies that, on aircraft with a steerable nosewheel, the locking scissors are set to full swivel for towing. The locking device must be reset after the tow bar has been removed from the aircraft. Persons stationed in the aircraft are not to attempt to steer or turn the nosewheel when the tow bar is attached to the aircraft.

5. Under no circumstances is anyone permitted to walk or to ride between the nosewheel of an aircraft and the towing vehicle, nor ride on the outside of a moving aircraft or on the towing vehicle. In the interest of safety, no attempt to board or leave a moving aircraft or towing vehicle is permitted. 6. The towing speed of the aircraft is not to exceed that of the walking team members. The aircraft’s engines usually are not operated when the aircraft is being towed into position. 7. The aircraft brake system is to be charged before each towing operation. Aircraft with faulty brakes are towed into position only for repair of brake systems, and then personnel must be standing by ready with chocks for emergency use. Chocks must be immediately available in case of an emergency throughout any towing operation.

8. To avoid possible personal injury and aircraft damage during towing operations, entrance doors are closed, ladders retracted, and gear-down locks installed. 9. Prior to towing any aircraft, check all tires and landing gear struts for proper inflation. (Inflation of landing gear struts of aircraft in overhaul and storage is excluded.) 10. When moving aircraft, do not start and stop suddenly. For added safety, aircraft brakes must never be applied during towing, except upon command by one of the tow team members in an emergency situation. 11. Aircraft are parked in specified areas. Generally, the distance between rows of parked aircraft is great enough to allow immediate access of emergency vehicles in case of fire, as well as free movement of equipment and materials.

12. Wheel chocks are placed fore and aft of the main landing gear of the parked aircraft. 13. Internal or external control locks (gust locks or blocks) are used while the aircraft is parked. 14. Prior to any movement of aircraft across runways or taxiways, contact the airport control tower on the appropriate frequency for clearance to proceed. 15. An aircraft parked in a hangar must be statically grounded immediately.

Taxiing Aircraft

As a general rule, only rated pilots and qualified airframe and powerplant (A&P) technicians are authorized to start, run up, and taxi aircraft. All taxiing operations are