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Illustrated technical information covering Vol 2 Over 800 multi-choice systems questions Close up photos of internal and external components Illustrated history and description of all variants of 737 Databases and reports of all the major 737 accidents & incidents History and Development of the Boeing 737 - MAX General flightdeck views of each generation of 737's Technical presentations of 737 systems by Chris Brady Detailed tech specs of every series of 737 A collection of my favourite photographs that I have taken of or from the 737 Press reports of orders and deliveries Details about 737 production methods A compilation of links to other sites with useful 737 content Study notes and technical information A compilation of links to major 737 news stories with a downloadable archive A quick concise overview of the pages on this site

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Boeing has issued a reminder to operators in a Fleet Team Digest (737NG-FTD-02-18001) to pass on to their crews about the correct procedure for setting takeoff thrust. It follows 8 confirmed aborted takeoff events in 2017 resulting from advancing the throttles before engines were allowed to stabilize at 40% N1.

An example of the consequences of not following this procedure can be seen in the Jet Airways 737-800 overrun at Goa on 27 Dec 2016, in which the final report states that: “Probable cause of the Accident: The PIC pressed TOGA when the thrust on no.1 engine was 40% and no.2 engine was 28% in deviation from SOP, which caused the No.1 engine thrust to increase at a faster rate than no.2 resulting in aircraft yawing towards right. In the absence of timely desired corrective actions including reject takeoff, the aircraft veered off the runway and continued to move in a semicircular arc on the undulated ground resulting in substantial damages to the aircraft.”

Path of VT-JBG

Boeing say that following a review of the flight data by CFM or Boeing, the root cause for these events was the engines not being stabilized at 40 percent N1, prior to advancing the thrust levers to takeoff thrust (autothrottle TO/GA).

The recommended procedure for setting takeoff thrust begins by manually positioning thrust levers to approximately 40% N1, which allows the engines to accelerate and stabilize at an intermediate thrust setting. This minimizes asymmetrical thrust when TO/GA is selected. If the intermediate thrust setting overshoots 40% N1 speed, it is not necessary to reduce N1 down to 40%. TO/GA can be selected after the engines stabilize at 40% N1.

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*** Updated 05 Aug 2023 ***

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Full details are in FCOM Vol 1 - Normal Procedures - Amplified Procedures - Takeoff Procedure

The FCTM (Chapter 3 Takeoff and Initial Climb - Initiating Takeoff Roll) also states:

“Allowing the engines to stabilize provides uniform engine acceleration to takeoff thrust and minimizes directional control problems. This is particularly important if crosswinds exist or the runway surface is slippery. The exact initial setting is not as important as setting symmetrical thrust. If thrust is to be set manually, smoothly advance thrust levers toward takeoff thrust.

Note: Allowing the engines to stabilize for more than approximately 2 seconds before advancing thrust levers to takeoff thrust may adversely affect takeoff distance.”

737 Engine Stabilization for Takeoff

Crews should set approximately 40% N1 and allow the engines to stabilize before pressing TOGA
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