Learjet 35 PTM Chapter 7 (Powerplant)

Question 1

What is the name of our engines, and what is their thrust rating?

Answer 1

TFE731-2-2B turbofan engines that produce 3,500 lbs of thrust at sea level up to 72 F.

Question 2

What is N1?

Answer 2

It is the speed of the fan section in front. In our case, it is a single stage axial fan.

Question 3

In the compressor section, how many stages do we have? (LP & HP)

Answer 3

LP: 4 Axial stages
HP: 1 Centrifugal stage

Question 4

Stall-surge protection is provided by an automatically controlled surge bleed valve. How does this work?

Answer 4

Basically, the surge bleed valve vents out extra pressure from the axial compressor to match the capacity of the centrifugal compressor under varying speeds.

It opens when at slow spool speeds and closes as it gets faster. The reason being… less fuel to the combustion chamber = less BOOM = less air flowing over the turbine = less power available for the centrifugal compressor - thus at slow speeds air needs to be vented to prevent compressor blades from stalling.

Question 5

How many stages are in our *turbine?

Answer 5

4: One axial HP stage, and Three axial LP stages

Question 6

What does N2 indicate?

Answer 6

%RPM of the HP Axial Turbine

Question 7

How many RPMs does our turbine actually spin???

Answer 7

30,000 RPM (Wikipedia - Garrett TFE731 Specifications)

Question 8

The transfer gearbox routes mechanical power to the accessory gearbox to drive what components?

Answer 8

(GHOST)
- Oil Pump
- Fuel Pump and Mechanical Governor in the FCU
- Hydraulic Pump
- DC Generator
- Starter

Question 9

How does a jet engine work?

Answer 9

…. Good practice at remembering and talking about the fundamentals.

Question 10

At sea level, the fan contributes ___% of the total rated thrust. At 40,000’, the fan contributes ___% of the total thrust.

Answer 10

60%; 40%

Question 11

Engine fan rotation is ___________, and core rotation is _____________. (Counterclockwise/Clockwise)

Answer 11

Fan rotates Counterclockwise
Core rotates Clockwise

Question 12

What kind of oil do we use?

Answer 12

Type II

Question 13

A red pop-out pin indicator provides visual indication of __________ _________.

Answer 13

Clogged Filter

Question 14

How is the oil cooled?

Answer 14

It is cooled by air and our fuel.

Oil is routed to our Air-Oil Coolers where air passes over oil cooling fins. Because our fuel is relatively cold, fuel is routed to a fuel-oil cooler that is mounted on the engine.

Question 15

If you start an engine with the inverters off, will you get an Oil Pressure Indication? If yes, great! If not, how can you find out if you have oil pressure?

Answer 15

No, it requires 26 VAC and will not be available if the inverters are turned off.
One way is to observe the small L/R LO OIL light extinguish once oil pressure is above 25 psi.

Question 16

What does the electronic fuel computer do in automatic mode?

Answer 16

1. Controls fuel flow.
2. Provides engine overspeed protection.
3. Controls the surge bleed valve.

Question 17

What are the five inputs to the electronic fuel computer?

Answer 17

N1
N2
ITT
PT2/TT2
Thrust Lever Angle

Question 18

What is the Start Pressure Regulator (SPR)? And when is it used?

Answer 18

Normally, fuel enrichment is automatically controlled by the fuel computer up to 200°C ITT. fuel enrichment may be extended manually using the SPR switch to assist engine start during cold temperatures (below 0°F). Make sure to release the switch when…

ITT indicates between 300°C and 400°C!!!

Question 19

When should you use your air ignitions? (AIR IGN L/R)

Answer 19

It may be used continuously while flying in heavy precipitation, icing conditions, or turbulent air. It must be used for takeoff and landings.

Question 20

What is the purpose of the soft start feature of our starters?

Answer 20

To limit the immediate load on the mechanical drive components. After 1.5 seconds the full electrical potential is available to complete the start.

Question 21

In sequence, what should happen when you are starting the engines and what do you look at?

Answer 21

(Open for edits)
1. START-GEN Switch is moved to Start.
2. N2 begins to rotate through 15%
3. N1 has positive rotation
4. Thrust levers move out of cutoff position to IDLE (AIR IGN lights illuminate)
5. Verify Fuel Flow is steadily increasing
6. Verify Oil Pressure is rising
7. Starter light extinguishes at 45%-50% N2
8. START-GEN Switch to OFF.

Question 22

Tell me about ENG SYNC

Answer 22

• You can slave the right engine’s N1 or N2 to the left engine.
• Anytime the nose gear is down and locked with ENG SYNC on, an amber ENG SYNC light will illuminate on the glareshield.
• The engine’s N1 or N2 need to be within 2.5% of each other in order to turn ENG SYNC on.

Question 23

What are the two types of thrust reversers we can have and what are the differences?

Answer 23

Aeronca
- Pneumatically Operated (Bleed Air)
- Has an Emergency Stow red rocker switch
- Max N1 is 60%
Dee Howard TR 4000
- Hydraulically Operated
- Has two switches that are labeled TEST-OFF-ARM
-Max N1 is 75%