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Home > Flying the Plane > Why doesn’t the pilot apply full power immediately at the start of take off?
Why doesn’t the pilot apply full power immediately at the start of take off?
Flying - Flying the Plane
Monday, 22 April 2013 04:32

Airbus A330-300 Jet Take Off – Cockpit View

Hi Captain Lim

I am a 32 year old Hong Kong guy and a sincere follower since I started reading your articles in the AirAsia in-flight magazine two years ago. Thanks for your website which gives me more useful information on aviation in my preparation for the Cathay Pacific cadet pilot programme.

I have one question about the aircraft's engine. Why doesn't aircraft pilot push the throttle to full power immediately when starting to take off? I have posed this question to others before but no one seems to be able to answer this question clearly.

I only know that the aircraft engine should be powered up to about 50% firstly and then full power after the 50% power have been achieved when taking off to reduce engine damage.

Would you mind giving me more information on this?

I am looking forward to your answer.

Yours sincerely

Neil

Hi Neil,

No one was able to answer your question clearly because it is not specific enough.

Take off techniques may vary from one aircraft to another. A similar plane may have two different types of engines installed. For instance, an Airbus A330 by one airline may use Rolls Royce engines and another one uses General Electric engines. Each plane with different engines has a slightly different technique.

Additionally, heavy weight, strong crosswinds and runway conditions (wet or contaminated) may affect how the power is applied during the take-off. As such, full power would or may be used in these cases.

However, when the passenger or cargo load is light, a different technique with FLX or partial power is used, mainly to reduce the wear and tear of the engines, and consequently saving of cost in terms of maintenance.

Below is an example of an Airbus A330 take off technique with GE engines based on two different conditions:-

a. If the crosswind is at, or below, 20 knots and there is no tailwind:

THRUST LEVER ....................................Full (TOGA) or Partial Power (FLX)

‐ To counter the nose-up effect of setting engine take-off thrust, apply half forward stick until the airspeed reaches 80 knots. Release the stick gradually to reach neutral at 100 knots.

‐ Pilot Flying progressively adjusts engine thrust in two steps :

• From idle to about 50 % N1.
• From engines at similar N1 to take-off thrust.

‐ Once the thrust levers are set to FLX or TOGA detent, the Captain maintains his hand on the thrust levers, until the aircraft reaches V1.

b. In case of tailwind, or if crosswind is greater than 20 knots :

THRUST LEVER on all engines.................Full (TOGA) or Partial Power (FLX)

‐ The Pilot Flying applies full forward stick.
‐ Pilot Flying sets 50 % N1 on all engines, then rapidly increases thrust to about 70 % N1, then progressively to reach take-off thrust at 40 knots ground speed, while maintaining stick full forward up to 80 knots. Release the stick gradually to reach neutral at 100 knots.
‐ Once the thrust levers are set to FLX or TOGA detent, the Captain maintains his hand on the thrust levers, until the aircraft reaches V1.

PS. To check for any latest updates or postings, you can follow my new Twitter at @CaptKHLim


Cockpit – Boeing 747-400 take off from Hong Kong

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Comments (7)

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Weather Forecaster new Zealand
I have followEd you sebsite for a long time with mY interest in aviation. I listen to Oceanic hf radio from all over the world and use Jeppersen charts to locate the waypoints... Despite data link technology there is still a lot going on on HF. Recently I came across Flightradar24.. Interesting stuff
Cheers Steve Wellington NZ
Steve Rawdon , 25 Apr, 2013
...
I had heard that the reason for pausing on a lower power setting initially was to check for any possible engine problems. Is this true?
John , 22 May, 2013
...
My understanding of what he was asking was "why do the procedures have you go to 50% N1, and then to takeoff power rather than directly to takeoff power?" My guess is to check the engines' operation first.
Ryan N. , 08 Sep, 2013
737-900 Capt.
Simply put, the answer is to ensure you have sufficient oil and hydraulic pressure at 40-50% N1 before advancing the throttles to full and discovering the hard way that you have a problem which may lead to engine failure on climbout.
Robert , 27 Sep, 2013
...
We advance to 40% prior to selecting takeoff power largely to guard against uneven engine spool-up. The 0-40% accel takes the longest, so it gives us plenty of time to ensure that the engines are working at the same rate. We hold at 40% for 2 seconds, then go for it.

Uneven spool up has been known to result in jets departing the runway as one engine starts pushing harder than the other. Not good!
B737 , 04 Jun, 2014
Inlet vortices
I believe another reason is to help prevent inlet vortices which can lead to compressor stall and possible engine damage. Inlet vortices are most likely to occur at high engine inlet airspeed / aircraft ground speed ratios; i.e. high power setting while stationary; This is more important in aircraft which have large engine inlets located close to the ground. Once there is some ground speed the inlet vortices are much less likely to form. In addition crosswinds can increase chances of a vortex, while a headwind will reduce it.
Henry , 13 Jan, 2015
Brake hold
I just flew out of Florence IT recently. Due to the runway config and nearby obstacles (mountains), it seems it can be necessary to take off with a tailwind. Our E190 was spooled up partway (per above 'warm up' if you will), then with the brake still set, spooled up to TOGA for maybe 1 second before brake release.
It was a very fun ride! Very little runway used, and a steeper than typical climb angle for the first couple 1000 feet of altitude. A great ride.
I can see why the E190 is used at LCY with their steep pattern.
RaflW , 19 Sep, 2016

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