The Lear 24 and 25 are pretty much the same except for the weights and some other minor differences.  I therefore chose to cover them both in the same study guide.  The Lear 23 and Lear 28, however, are different  in some ways that can hurt you if you don't know about them, so I provided separate study guides for them.

   * All weight in excess of the Max ZFW must be fuel in the Wing and tip tanks.

  The above weights are maximum certificated limits.  The actual maximum weights for a particular flight may vary a great deal due to performance limitations.  If the aircraft can not meet the required "Takeoff Field Length" and "Climb" limitations, (engine out climb performance), the maximum takeoff and/or landing weights are reduced such that the requirements are met.  See the performance charts in the AFM for details.

 Speeds

  Yaw Damper Off for T.O., On for Flight, Optional for LDG
 Airplane shall be configured for landing by 500 ft AGL

Lear Jet

Note: 100% = 16,500 Rpm

 Engine Oil System Limitations
 

Note:  Idle for 3 Minutes prior to takeoff if ambient temp is below - 25 C
See AFM for Approved oils. Do not mix brands of oil.
 

Systems
 

Primary Flight Controls
    The ailerons, elevator and rudder on the Lear Jet are manually actuated by the pilots.  Aileron and rudder trim is achieved with trim tabs on the rudder, and left aileron.  These trim tabs are positioned by electric motors located inside the left aileron and the rudder it's self.  Pitch trim is achieved by changing the position of the moveable horizontal stabilizer.  There are two trim motors that will do this, a primary, and a secondary.    The aileron, rudder, and primary pitch trim are controlled with a thumb switch on the left side of the Capt.'s and right side of the Co-Pilot's control yoke.  The secondary trim is actuated by the autopilot, and can be controlled by an  electric switch on the console in the event the primary trim fails.
    The aircraft does have an autopilot, although not a very good one until you get to the 31, 45, 55 or 60.  The ailerons and elevator may be moved by the autopilot servos, and the rudder is equipped with a primary and secondary yaw damper.  Both yaw dampers are required for flight although only one may be engaged at a time.
    The Lear Jet has two stall warning systems.  They are the same.  Both are required for flight.  Angle of attack information is given to the system by two angle of attack vanes located on the left and right sides of the nose of the aircraft.  These vanes are heated when the pitot heat switch is on.  They get hot enough to burn you, so touch them with caution.
    About 7% above a stall, the system warns you with a flashing stall warning annunciator light, and by activating the stick shaker.  At about 5% above a stall, the autopilot pitch servo applies an 80 pound push on the elevator.  If you do not notice this, you deserve to crash!  It is hard to ignore.
    There is a "Wheel Master" button just below the trim actuator on each pilot's yoke.  It  is a handy little guy.  It interrupts any elevator trim action, deactivates the stick pusher, disengages the autopilot, and will engage the nosewheel steering if the gear is down.

 The trim check very important on the Lear Jet, as the trim system on this aircraft, if not properly set can KILL you within seconds after liftoff.  Excuse the lack of tact here, but it's a fact.  Perform the trim check prior to takeoff.

Flaps
    The flaps on the Lear are hydraulically actuated.  The flaps are controlled in one of two ways, depending on the model lear.  Most have one switch with three positions, Extend, retract, and off.  Select extend, or retract until the flaps are in the desired position, then select off.  Some Lears have preselect where you place a lever in the desired flap position, and the flaps extend to the position requested.  If the flaps will not extend, add 30 kts to your approach speed and 30% to your landing distance.
    There is pressure relief valve in the flap system that will prevent damage to the flaps if they are inadvertently extended or left down at speeds in excess of their operating limitations.

Spoilers
    Lear Jets are equipped with spoilers.  They may be deployed up to Vmo / Mmo in flight only when the flaps are retracted.  On landing, they should be deployed just after touchdown.  They are hydraulically actuated, and electrically controlled.  They have two positions, fully deployed, and stowed.

Nosewheel Steering
    The nosewheel steering on the Lear is electric.  It requires both AC and DC to operate.  Steering is engaged with the wheel master switch, or by a "Steer Lock" switch on the left side of the Capt.'s panel on 20 series airplanes, and the center pedestal on 30 series and later models.  Maximum speeds for use of nosewheel steering is either 45 knots, or 10 knots, depending on the steering mode selected, and / or loss of wheel speed input from more than one of the right three main wheels.  See AFM for details.

Landing Gear
    Like all other aircraft intended for more than one flight, the Lear jet has a landing gear.  It is extended and retracted hydraulically, and controlled electrically.  It can be extended with high pressure nitrogen if the normal extension fails.

Brakes
    Each main landing gear on the Lear Jet has two wheels and tires.  Each wheel has it's own hydraulic brake, with anti-skid protection.  The brakes on the left gear are controlled by pressure applied to either of the left brake pedals, and the right brakes work the same way from the right pedal pressure.  The anti-skid system can relieve the brake pressure on any individual wheel.
    If the hydraulic brake system fails, there is an alternate brake system that will apply the brakes with high pressure nitrogen.  The same bottle is used for emergency gear extension.  The emergency brake system does not provide any anti-skid, or differential braking capability.  It is a good system, and if you use it with your brain engaged, it works fine.

Lear Jet Fuel System Schematic

Fuel Capacity

Lear Jet Hydraulic System Schematic

    The Lear Jet hydraulic system consist of  2 engine driven, and one electric hydraulic pump, a 1.9 gallon reservoir, an accumulator (two accumulators if Dee Howard reversers are installed) and a couple of pressure relief valves.  The fluid is 5606 therefore if you spill some on yourself, you won't wind up looking like you and Michael Jackson share the same dermatologist.  The system operates the landing gear, normal braking with anti-skid, the flaps, spoilers, and thrust reversers (except aeronca) if the aircraft is so equipped.
    The reservoir is pressurized by bleed air on later models, and cabin air on earlier Lears.  This is to prevent foaming.  The engine driven hydraulic pumps can only access 1.5 of the 1.9 gallons of hydraulic fluid.  The additional 0.4 gallons can be used by the electric hydraulic pump only.  It can extend the landing gear, the flaps, provide normal braking with anti-skid, and on the 20 seriesonly, extend the spoilers.  The hydraulic thrust reversers have their own accumulator, and should be useable even with total hydraulic failure.
    The system has two pressure relief valves, one main system relief valve, that relieves at 1700 to 1750 psi, and one relief valve in the flap system that relieves about 1650 psi.  See "Flaps' in the flight controls section for more details on this.
    With total hydraulic system failure, blow the gear down, approach at Vref + 30 kts, use pneumatic brakes, and plan on 1.7 to 2.0 times your normal landing distance.  T/R's may work!
 
 

DC Electrical
    The Lear Jet 20 series electrical system consists of two 24 or 25.2  volt batteries, two 400 ampere starter / generators, left and right DC Busses, and two 275 Amp current limiters.  Current limiters are nothing more than slo-blo fuses.    The current limiters connect the generators to the battery bus.  The starting current goes through the start relay, and does not pass through the current limiter.  The current that recharges the batteries does.  If you blow a current limiter other than due do an electrical short, it will probably be just after engine start when you put the first generator online.  Because the batteries are in a somewhat depleted  state after starting an engine, they want all of the electrons they can eat.  This is sometimes more than the current limiters can take.
    The AC power on these aircraft is supplied by two, or sometimes three inverters.  On the two inverter systems, one of the inverters can supply the entire AC system.  The three inverter systems use smaller inverters.  If one fails, select the standby inverter to replace the failed main inverter.
 
 

Lear Jet Electrical System

Current Limiter Check
     The current limiter check tests the current limiters to verify that they have not been blown.  The time you are most likely to blow a current limiter is immediately after engine start, when the batteries are low.  The generator is put on line, and the "hungry" batteries (Ni-Cad's) wish to recharge themselves ASAP.  They can draw 300 to 400 amps or more. This is more than the poor 275 Amp current limiter can take for longer than a moment, so it blows.  Cut down in the prime of life!  A blown current limiter could prevent you from resetting a tripped generator under some conditions.  If you have a blown current limiter, replace it prior to departure.   After both engines are started and generators are on line, check the current limiters as follows:

1.  Pull the "Main DC Bus Tie" breaker
2.  Take the left generator off line and check that the right generator picks up the load.
     Check that left DC bus   items are powered.  If so, left current limiter is OK.
     Reset left generator.
3.  Take the right generator off line and check that the
     left generator picks up the load.  Check that the right DC bus items are powered.
     If so, the right current limiter is OK.  Reset right generator.
4.  Reset the "Main DC Bus Tie" breaker.

     ** Current Limiter Check is Complete **

    The standby battery switch has three positions: OFF, STANDBY, and ON.  In the ON position the emergency battery powers the small third attitude indicator, it's light, and the control circuits for the landing gear and flap systems. The three green landing gear lights are also powered by the emergency battery, and will illuminate when the gear is down and locked.  The red "gear door not locked" lights are not powered by this battery.  In standby, it powers just the gyro and it's light.  Most of these batteries will charge in the ON and Standby positions, however, some, such as the ones in the Lear 28 must be left "ON" to be charged.   Some later model aircraft may be equipped with a second standby battery.  This will usually power an emergency comm radio, and whatever other devices the customer would like.

If you experience loss of all main DC bus power for any reason, remember the following:

 1.  Emergency battery switch to ON.  Landing gear extension will be normal
      except for the loss of the red gear door warning lights.
 2.  Landing gear warning horn will be inop.
 3.  Engine stator and nacelle lip heat are on.
 4.  Wing and tail anti-ice, pitot static, and angle of attack probe heat will be inop.
 5.  Windshield Heat will fail in the last position selected.
 6.  Tank to tank fuel transfer will not be possible if crossflow valve
       was closed at time of power loss. If crossflow valve was open, the
       boost pumps will fail, making pressure fuel transfer impossible, however,
       the crossflow valve will remain open, allowing some fuel transfer due to a
       very reliable power source called gravity.
 7.  The AC electrical system will be inop as it receives it's power from the DC system.
 8.  The hydraulic system will be inop, except for the landing gear and flaps, as their
       control circuitry is powered by the emergency battery when the "ON" position
       is selected.
 9.  Nosewheel steering  will be inop, as it requires both AC and DC electrical power.
10.  Anti-Skid system is inop.

These things may require some thought as to how one wishes to conduct the remainder of a flight.

Normal Operation:
     Battery switches ON, before engine start, all DC busses are powered by batteries or GPU.  After engine start, all busses are powered by the generator(s), and the batteries are recharged.

Battery Overheat
     Respective battery switch OFF. This prevents battery charging.  DC busses powered by generator(s).  Monitor temp of offending battery.  If your lear does not have dual battery switches, use the battery disconnect switch for the offending battery.  All 30 series and later Lears have dual battery switches.

"AC" Electrical System
    A Lear Jet is usually equipped with two inverters.  A third inverter is an option on Lear 24's and all later Lear Jets.  Almost all of the Lear 30 series are equipped with two solid state inverters.  Either one can supply AC power to all items on the aircraft that require it.  They normally operate in parallel, but if one fails, the other picks up the remaining load automatically.  An AC paralleling unit aligns the phase of the two inverters to make them work in parallel.
    The AC items on the Lear include:  Gyros, Autopilot, Altitude Alert, Mach trim system, Nosewheel Steering, Engine pressure gauges, and a few other items that vary from aircraft to aircraft.

    Most 20 series, and all later Lear Jets are certified for flight into known or forecast icing conditions.  Starting from the front of the airplane, the radome is anti-iced by alcohol that is pumped onto it through a plastic nozzle located at the very front of the airplane.  The same alcohol pump provides emergency anti-ice for the left windshield.  You have about 90 minutes for the radome, and 45 minutes for the radome and windshield together.
    The pitot tubes, static ports, and angle of attack vanes are electrically heated, controlled by the "Pitot Heat" switches in the cockpit.  The windshields are heated with engine bleed air.  The wing leading edges are heated by bleed air.  The horizontal stabilizer has an electric heating element attached to it's leading edge.  This draws about 90 amps when used.
    Engine nacelles are electrically heated, and the stators and engine front frame is heated with bleed air.  On the "Non Ice" lears, if you lost one generator, you lost the heat to that nacelle.  ECR 771 fixed that, as well as added the radome anti-ice in order to gain certification for known ice operation.
 

Lear Jet Environmental System

Note:  The individual bleed air switches are not installed on most of  the earlier airplanes.  A check valve on each side kept one engine from pressurizing the other.
           In some cases, the early aircraft had two switches that controlled airflow to the cabin.  Instead of the one switch, "OFF, NORM, MAX", there were two
           switches, one "ON or OFF", and one "NORM or MAX".  Each controlled the folow control valve in the same way.

    The Lear 20 series aircraft are pressurized, like most airplanes, by engine bleed air.  This air comes from the 8th stage compressor on the engine through a heat exchanger in the tailcone of the airplane, and is cooled, then goes into the cabin.  Temperature is regulated by a "Damper Valve".  This valve controlls the ambient airflow across the non pressurized side of the heat exchanger.   Temperature is regulated by a "Damper Valve".  This valve controlls the ambient airflow across the non pressurized side of the heat exchanger.  This does not provide enough cooling for low altitude and hot weather, so a freon airconditioner is provided for use below 18,000 feet.
    Emergency pressurization air is provided by way of the windshield heat system.  Place the defog knob so the windshield air goes to the inside of the airplane, and you have another source of air for pressurization.  This system bypasses the flow control valve and heat exchanger.
    On the outflow side of things, the cabin pressure is regulated by a main outflow valve, located at the forward end of the pressure vessel.  The automatic pressurization system requires DC power on all but the earliest 20 series airplanes.  In the event the automatic pressurization fails, cabin pressure may be controlled pneumatically, by the "Cherry Picker" that uses air to move the outflow valve.  Maximum differential  relief between 9.12 and 10 psi, and negative pressure relief at -  0.25 psi, and positive pressure depending on the model and serial number airplane.  This "Safety outflow valve" is strictly mechanical.  It requires no electrical power.
 
 

Flight Profiles

    Here are some basic flight profiles that I have used over the years.  They are not the only way to fly the airplane, but have worked for me since I started giving training and checkrides in the Lear a little over 20 years ago.  In the event of a difference between this and the Aircraft Flight Manual, the flight manual is the document to follow.

Steep Turns

1.  Enter at 250 KTS indicated AIRSPEED.
2.  Bank aircraft 45 deg.  As you pass 30 deg of bank, pitch up 2 deg.  Add power to maintain AIRSPEED.
3.  Lead roll out by 15 deg.  Passing 30 deg bank, pitch down 2 deg  to maintain  altitude.
4.  Maintain 250 KTS and assigned heading.

Stall - Cruise Configuration

1.    Compute Vref & set AIRSPEED bugs.
2.    Maintain assigned altitude and set power to Idle.
3.    Trim for level flight until passing 150 KTS.  Maintain altitude with necessary back pressure.
4.    At stick shaker or stall warning lights,  throttles to " MAX POWER "
5.    Call " MAX  POWER Flaps Approach.
6     Reduce pitch ONLY to the extent necessary to eliminate symptoms of the stall.
7.    Reestablish assigned altitude.
8.    At Vref + 30 KTS, call " Flaps Up, After Takeoff Checklist.  "
9.    Maintain AIRSPEED and altitude as directed.

Stall - Takeoff Configuration

1.  Compute Vref, set AIRSPEED bugs & select flaps 20.
2.  Maintain assigned altitude and set power to 65% N1.
3.  Trim for level flight until passing 150 KTS.
4.  Maintain altitude with necessary back pressure.
5.  At stick shaker or stall lights, advance throttles & call " MAX POWER ".
6.  Reduce pitch ONLY to the extent necessary to eliminate symptoms of the stall.
7.  Reestablish assigned altitude.
8.  At Vref + 30 KTS, call " Flaps Up, After Takeoff Checklist.  "
9.  Maintain AIRSPEED and altitude as directed.

Stall - Landing Configuration

  1.  Slow to flap speed, set 80% N1 & Set bug to Vref.
  2.  Maintain assigned heading & altitude.
  3.  Below 193 KTS, " Flaps 20 deg".
  4.  " Gear Down Landing Check ".
  5.  Below 150 KTS, " Full flaps. " trim to Vref. Establish a 400-700 feet/min sink rate at Vref.
  6.  Level off at designated altitude  W I T H O U T increase in power
  7.  Maintain altitude until  first indication of a stall. (Shaker or stall lights)
  8.  Apply MAX power lower nose only as much as required to eliminate the stall warning.
       At Vref minus 10 KTS   M I N I M U M  speed, call for " Flaps 20 deg", and increase the
       pitch attitude to 10 deg nose up at about 1 deg / sec.
  9.  When VSI & Altimeter indicate positive rate of climb call " Positive rate, Gear Up ".
10.  Establish 7.5 deg nose up attitude.
11.  At Vref + 30 KTS, Call " Flaps Up, After Takeoff Checklist ".
12.  Return to entry heading and altitude or as directed.

ILS Approach - Two Engines

1.  Intercept LOC at 140-160 KTS and Flaps 20 deg.
2.  One dot prior to intercepting Glide Slope, call " Gear Down Landing Check ".
3.  When ON the glidepath, call " Full Flaps ".
4.  Establish Vref to Vref + 5 KTS & track LOC & GS until Minimums.

ILS Approach - One Engine

 1.  Intercept LOC at 140-160 KTS and Flaps 20 deg.
 2.  When Intercepting the glidepath, call " Gear Down Landing Check ".
 3.  Establish Vref + 20 KTS & track LOC & GS
 4.  At 100-150 Ft AGL, Full flaps, power idle & land.

Non Precision Approach - One or Two Engines

1.    Intercept Final Approach Course at 140 KTS and Flaps 20 deg.
2.    Crossing Final Approach Fix, call " Gear Down Landing Check ".
3.    Descend to and maintain MDA until Field in Sight or MAP is initiated. ( As Appropriate ).
4.    If Landing is to be made, call " Full Flaps " when intercepting a glidepath appropriate for a
       normal landing.  For one engine INOP, Vref + 20 KTS until 100 feet AGL, then " Full
       Flaps" so as to descend thru 50 ft AGL at Vref as in a normal landing.

No Flap Approach

1.  Vref + 40 KTS until established on Final Approach.
2.  Vref + 30 KTS on final.
3.  Approach angle NORMAL.  A flat approach will usually result in a longer landing roll.

Go Around or Missed Approach

1.  "Max Power", Rotate to 10 deg, " Flaps 20 deg".
2.  Positive Rate of Climb, " Gear Up ", Vref + 30, " Flaps up, After Takeoff Checklist ".
3.  Climb at 200 KTS.
4.  Engine Failure or Fire Checklist if Appropriate.

Takeoff

1.  Set V2 on Capt. Airspeed & V1 on Co-Pilots Airspeed.
2.  At V 1, BOTH hands on Yoke.
3.  Vr, Rotate to 15 deg ( 2 eng ) 12 deg ( 1 eng ).
4.  Climb at 15 deg pitch, ( 2 eng ) or V 2 ( 1 eng ).
5.  At 400 ft & V2+30 KTS, "Flaps Up After T.O. Check ".
6.  Engine Failure or Fire Checklist if Appropriate.
7.  Climb  200 KTS to 3000 AGL then 250 Kts.

Rejected Takeoff

1.  Proceed as in normal takeoff until malfunction dictates that the takeoff be rejected.
2.  Capt. calls "Abort" (Co-Pilot may call Abort if Capt elects to delegate that authority).
3.  Thrust levers to idle
4.  Spoilers extend.
5.  Wheel brakes as necessary.
6.  Thrust Reverse OR Dragchute deploy.  (Never Both at the same time!!)
7.  If another takeoff is contemplated consider brake energy & appropriate turnaround time.

Emergency Descent

 1.    Oxygen masks on within 5 sec of cabin pressure loss.
 2.    Check passenger oxygen masks deployed.
 3.     Select Oxygen mask microphone.
 4.    Ignition ON.
 5.    Thrust levers to idle.
 6.    Spoilers and Landing Gear, Extend.
 7.    Auto Pilot OFF.
 8.    Initiate 45 deg bank if desired.
 9.    Vmo/Mmo minus 10 kts to 14,000 or MEA as required.
10.  Clean up & proceed to nearest suitable airport if appropriate.  Condition of aircraft or
        reduced range due to low altitude may make flight to original destination unwise.

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