737 Aviation

Let's see what's inside

Fly Safe!

Boeing 737 flap retraction. #aviation #boeing #flight

MSFS 2020 getting more and more realistic

Hi All!

First look into BlackSquare Piston Duke!

LINK IN COMMENTS!

Fly Safe!

https://www.youtube.com/watch?v=dAVWUN8QFQ4

Coming Soon! :)

✈ Boeing 787-9 - Microsoft Flight Simulator 2020 Abu Dhabi - Muscat || Real Boeing Captain || Welcome aboard our virtual Etihad Airways flight! Join me, a Boeing 737 Captain, as we take off from Abu Dhabi International Airport (AUH) in the state-of-th...

Full approach with ATC!

LINK IN COMMENT!

Fly Safe

Hi All!
Soon we will get back to the Microsoft Flight Simulator 2020, and I'd like to invite you to join me during this event!

Fly Safe!

Hi All!

New Video today.!

LINK IN THE COMMENTS.

Fly Safe!

Hi All!

You might have noticed some period of inactivity on the Channel, that was due to high summer season and working on the other project such as the one below. Despite it is in Polish, there are subtitles availiable in English and other langiages and you are more than welcome to join us in the adventure!

More activity in English to come soon to 737Aviation.

LINK IN THE COMMENTS!

Fly Safe!

It's quite hard to discuss reliability of this information at that stage, but that's what WSJ reports....

China Eastern Black Box Points to Intentional Nosedive

Hi All!

First video of MG Honda Jet in MSFS2020

Fly Safe!

✈ Honda Jet - Microsoft Flight Simulator 2020 - Live Virtual Flight || Real Honda Jet Captain || Hi All!Today I will present you with a brand new Honda Jet HA420 addon to MSFS2020. The airplane is created by Marwangharib and you can find more detail on h...

Hello guys,

Come on and check our another live on B737 Classic!

✈ 737Aviation - Virtual Flight || Real 737 Captain flies 737 Classic || Hi All!On the begining little disclaimer, it was supposed to be a live stream but unfortunetelly I got stuck with rather poor internet connection so only thi...

ENGINE STARTUP AND ASSOCIATED PROBLEMS

Have you ever wondered what may happen during B737NG (CFM 56-7B)
engine startup ? Actually there are a variety of possible issues and in this article We will describe some of them..

Firstly, How does it work ?

Basically, to perform startup you need bleed source, electrical power and fuel. Firstly, you put start switches to GRD and that allows the pneumatic starter to operate and rotate the N2 shaft via accessory gearbox. Then you observe an increase in N2 rotational speed percentage and when it reaches approximately 25% or maximum motoring at 20% N2 (when N2 increases by less than 1% in 5 seconds) you put the start lever to the IDLE position. This engages igniters and starts fuel flow to the combustion chamber. Normally N1, EGT, oil pressure and temperature increases, and when N2 reaches 56% starter cuts out and engine stabilises at idle.

Starter duty cycle is limited to 2 minutes, and at least 10 seconds is required between subsequent start attempts.

Standard day, sea level, approximate stabilized idle indications for CFM56
engine.
• N1 RPM – 20%
• N2 RPM – 59%
• EGT – 410°C**
• Fuel Flow 272 KGPH

**Idle EGT may vary from 320°C – 520°C depending on OAT, bleed
configuration, and engine conditions.

During the startup, you must closely monitor all engine parameters and hold a hand on the fuel handle to abort that process when any parameter is approaching or exceeding limit or simply something is going wrong.

If the decision to abort engine startup is made due to these reasons, perform ABORTED ENGINE START NNC!

-No N1 (before the start lever is raised to idle).
-No oil pressure (by the time the engine is stable).
-No EGT (within 10 secs of start lever being raised to idle) [Wet Start]
-No increase, or very slow increase, in N1 or N2 (after EGT indication).
EGT rapidly approaching or exceeding 725˚C [Hot Start]

If engine startup is aborted due to no oil pressure when engine is stable at IDLE, it must be motored for 60 seconds. Damage to the bearing at low N2 is not likely to happen, but removing heat from the core is very important.

During GROUND startups, EEC provides abnormal start protections, which we will describe below.

1. Hot Start

Hot Start occurs when the engine approaches the EGT start limit (725 C) rapidly or exceeds it. Impending hot start may be detected by abnormally rapid rise in EGT.

When EEC detects abnormal rise of EGT or limit approaching EGT white box will flash (it resets when lever is moved to CUTOFF or engine reaches idle N2). After exceedance occurs the box and dial remains red to remind crew about exceedance.

Newer EEC software versions (7.B.Q. or later) automatically cuts off ignition and shuts fuel after impending hot start or N2 compressor stall detection.

Possible causes of hot start:

-Prematurely start lever to IDLE detent (newer -FCU software versions as installed inhibits fuel flow below 20% N2)
-FCU issue
-Early starter cutout
-FOD or engine internal damage
-Faulty EEC (illumination of MASTER CAUTION+OVHD+ENGINE CONTROL during startup may inform you about impending hot start!)
strong wind (especially tailwind)
-Off scheduled Variable Stator Vane (VSV)

Additional note : If FF (fuel flow) indicates above 0.35 (350kg/h) after the start lever is raised to idle, you should be aware of possible hot start! Newer FCU software makes a short peak of 0.75(750kg/h) to raise the chance of successful light up, but then it should come back to 0.35(350kg/h)!

Serious EGT exceedance during startup may lead to engine severe internal damage!

2. Wet Start

During heavy rainfall the engine might have some problems with lighting up. When EGT does not increase despite positive fuel flow you are facing the wet start. Also igniter fault or EEC ignition control function issue may result in wet start.

During wet start EEC also provides ground start protections. If EGT does not increase within 15 seconds from raising start lever to IDLE (20 seconds if OAT is below 2 C) it will turn off ignition and shut fuel.

If there is a problem with the igniter, you may try placing the ignition selector to both. If the engine lights up normally after placing both, that's just a problem with the firstly selected igniter. With left ignition INOP you may continue normally, however you CANNOT dispatch with right ignition inoperative, maintenance is required.

3. Hung Start

Hung Start may be recognized by engine N2 RPM stagnant at around 60% with EGT increasing. During that condition the engine is unable to stabilise at idle.

It may be caused by:

-Negative fan rotation, due to tailwind.
-insufficient fuel flow due to eg. malfunctioning FCU or HMU
-excessive bleed extraction (packs or anti-ice ON)
-FOD or turbine damage

To stop negative fan rotation you may use reversers, however you must keep in mind that it is not authorized procedure, and you must ensure that ground personnel are not in danger and you have to take into account that it may result in fault in deploy/stow logic.

4. Start valve does not open

During cold days, the start valve might be freezed and stuck, resulting in inability to open. You should call maintenance and ask them to open the cowl and heat the starter valve using hot air.

If the solenoid is stuck itself, the mechanic may open the start valve by inserting a pin into a hole near the gen drive access door.

https://youtu.be/en4LUIwykzA

You should also check the start valve C/B’s. If START VALVE OPEN does not illuminate despite normal N2 acceleration you should suspect start valve open indication fault and dispatch as per MEL 80-01.

5. Start valve does not close

If starter simply does not shut automatically after reaching approx. 56% N1 you should place it OFF manually and if START VALVE OPEN light extinguishes, you may dispatch as per MEL 80-02 (engine starter auto cutout INOP), if it does not accomplish START VALVE OPEN NNC!

If the duct pressure comes back to pre start value you may suspect faulty start valve indication system and dispatch as per MEL, however if the pressure remains as for open starter and light is illuminated, DO NOT shut down engine by recall (placing start lever to CUTOFF), because you will blow up the starter due to very high pressure! You must first isolate the air source as per NNC, and then shut down.

6. No engine rotation

If the rotational speed of N1/N2 shows zero you must abort startup. There are some possible reasons behind that:

-Shaft Seizure (N1,N2 or starter)
-N2 indicator/tachometer failure - no MEL, nogo
-N1 indicator/tachometer failure - dispatch as per MEL 77-02
-Strong Tailwind causing fan to negative rotation.
excessive bleed extraction

7. Leaks

If the ground crew warns you about an engine leak, shutdown the engine. Then restart it, and:

-If the leak continues after the second start, maintain idle thrust for
up to 5 minutes.
-If the leak stops within the 5-minute window of second start, no
maintenance action is needed.
-If the leak continues, or at any time becomes significant, shut down
the engine and call maintenance

As you can see, engine startup is a complicated process during which you may encounter a variety of problems so always treat it seriously and follow procedures!

To sum up, watch a great video showing all described above engine start abnormalities from engine indications on DUs view!

https://youtu.be/5rB1-p9loBA

Sources: B737MRG by Captain Pat Boone, B737NG FCOM, B737NG AMM

Author: Łukasz Hinc

Fly Safe!