Technical Interview 5 Flashcards
If the engine driven pump failed, how would you lower the gear?
With the electric driven pump.
How many hydraulic systems does the Boeing 737 have?
The airplane has three hydraulic systems: A, B and standby. The standby system is used if system A and/or B pressure is lost. Either A or B hydraulic system can power all flight controls with no decrease in airplane controllability.
The hydraulic systems power the following airplane systems:
- Flight controls
- Leading edge flaps and slats
- Trailing edge flaps
- Landing gear
- Wheel brakes
- Nose wheel steering
- Thrust reversers
- Autopilots
Both A and B hydraulic systems have an engine–driven pump and an AC electric motor–driven pump. The system A engine–driven pump is powered by the No. 1 engine and the system B engine–driven pump is powered by the No. 2 engine. An engine–driven hydraulic pump supplies approximately 4 times the fluid volume of the related electric motor–driven hydraulic pump.
Components powered by hydraulic systems A and B are:
System A:
- Ailerons
- Rudder
- Elevator and elevator feel
- Flight spoilers (two on each wing)
- Ground spoilers
- Alternate brakes
- No.1 thrust reverser
- Autopilot A
- Normal nose wheel steering
- Landing gear
- Power transfer unit (PTU)
System B:
- Ailerons
- Rudder
- Elevator and elevator feel
- Flight spoilers (two on each wing)
- Leading edge flaps and slats
- Trailing edge flaps
- Normal brakes
- No.2 thrust reverser
- Autopilot B
- Alternate nose wheel steering
- Landing gear transfer unit
- Autoslats
- Yaw damper
You have lost both alternators, how long would the battery last and what would you do?
Note: this question was asked to a candidate with previous Warrior PA28 and Seneca experience, make sure to be able to answer this question for your previous aircraft type.
DA42: If both alternators fail at the same time, I would reduce all electrical equipment to a minimum, expect battery power to last 30 minutes and land the airplane as soon as possible. Expect engine stoppage after this period of time.
Why are swept wings effective?
On a straight wing airplane, all of the airflow over the wing travels parallel to the aircraft’s chord line. But,on a swept wing, only some of the air flows parallel to the chord line. The other part flows perpendicular to the chord - this is calledspanwise flow.
Only the component of airflow flowing parallel to the chord line accelerates. So, by reducing the amount of airflow flowing parallel to the chord line, you’ve reduced the amount of acceleration - and increased your critical Mach number.
At low speed a swept wing is not effective, at high speed they are effective.
When you reduce the amount of air flowing parallel to the chord line, you reduce the amount of lift the wing creates. At high speed, this isn’t a problem - your high airspeed requires a small angle of attack to create lift.However, at slow speeds, you’re at a high angle of attack, and sweeping the wing can force a very high angle of attack - nearing your stalling angle of attack.
What wings does the Boeing 737-800 use?
The 737 has swept back wings with an angle of 25º
For each wing, leading edge devices consist of:
- Two Krueger flaps inboard of each engine, because they are less efficient than slats and promote a root stall (swept-back wings have a tendency to stall at the tip first). This helps maintain aileron effectiveness and prevent the loss of control that can occur during a stall.
- And four slats outboard of each engine. The difference between krueger flaps and slats is that deploying a slat will form a slot (re energise (increase the kinetic energy of) the boundary layer), deploying a Krueger flap does not.
The TE devices consist of double slotted flaps inboard and outboard of each engine.
Each wing has 4 flight spoilers and 2 ground spoilers. In flight, spoilers are used as speed brakes, to slow the airplane or increase the rate of descent, or automatically to help the ailerons in roll control On the ground, ground spoilers destroy lift and increase braking efficiency, they operate together with the flight spoilers.
Winglets are vertical aerofoils which partly block the air flowing from the bottom to the top surface of the wing, reducing the strength of the tip vortex, thus reducing induced drag and fuel burn
Winglets on the 737-800 have demonstrated drag reduction in the 5-7% range, which increases range and fuel efficiency
What can you tell about the Boeing 737-800 electrical system?
- Primary electrical power is provided by two engine integrated drive generators (IDGS) which are rated at 90 KVA (kilo-volt amps) and supply three-phase, 115-volt, 400 cycle (Hz) alternating current.
- The battery is a 36 ampere-hour, 24-volt, nickel-cadmium battery and should provide around 30 minutes standby power if all other generators fail.
- Auxiliary Battery – This is a reserve battery on the 737NG which is normally isolated unless the main battery is powering the standby system, the auxiliary battery combined with the main battery can provide 60 minutes of standby power.
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The system generates alternating current, direct current, and standby power.
Primary electrical power is provided by two engine integrated drive generators (IDGs) which supply three-phase, 115 volt, 400 cycle alternating current. Each IDG supplies its own bus system in normal operation and can also supply essential and non-essential loads of the opposite side bus system when one IDG is inoperative. Transformer rectifier (TR) units and the main battery/battery charger supply DC power. The main and auxiliary batteries also provide backup power for the AC and DC standby system. The APU operates a generator and can supply power to both AC transfer busses on the ground or in flight.
There are two basic principles of operation for the 737 electrical system:
- There is no paralleling of the AC sources of power.
- The source of power being connected to a transfer bus automatically disconnects an existing source.
The electrical power system may be categorized into three main divisions: the AC power system, the DC power system, and the standby power system.
What are the G-limits of the Boeing 737-800?
With Flaps Up +2.5g to -1.0g
With Flaps Down +2.0g to 0.0g
What is a METAR?
METAR stand for Meteorological Aerodrome Report
METARs contain coded messages with the actual weather conditions at a given aerodrome at a stated time.
What is the fuel consumption of the Boeing 737?
2000-2600 kg/h
What is density altitude? and what is pressure altitude?
Pressure altitude is the indicated altitude when an altimeter is set to 1,013.2 mb. This is the altitude above the standard datum plane, which is a theoretical plane where air pressure (corrected to 15°C) equals 1013 mb (29.92 in.Hg). Its important as a basis for determining airplane performance.
Density altitude is pressure altitude corrected for air temperature.
What powers the gear? What is the PSI of the system?
The hydraulic system powers the landing gear.
3000 PSI.
What is the fuel capacity of the Boeing 737–800?
26.025 liters or 20.896 kgs
Fuel density = 0.8029 kilograms per liter
What are the hydraulic systems of the Boeing 737 called?
The airplane has three hydraulic systems: A, B and standby.
How do you get out of a spiral dive on a Cessna?
Note: make sure to be able to answer this question for your previous aircraft type
A spiral dive can be defined as a steep descending turn with the airplane in an excessively nose-down attitude and with the airspeed and g-load increasing rapidly.
Important factor is to maintain the bank angle below 90°.
Spiral Dive Recovery Technique:
- Reduce power to IDLE
- Roll to wings level with coordinated use of ailerons and rudder
- Use elevator inputs to bring the airplane to straight and level flight (keeping in mind that at the high airspeed you risk structural failure)
- When slowed down to a safe airspeed apply throttle as needed.
What is the cabin altitude of the Boeing 737 on a cruise flight level?
Normally around 6000 - 8000 ft (11 - 12 psi)
