LEFT: Captain-side B737 trim tabs with backlighting turned on (OEM throttle quadrant).
The sheer volume of information available on the Internet often results in ‘information overload’ and it is understandable that many become bewildered to the correct way of completing a task. The boundaries between fact and fiction quickly become blurred. Add to this that many articles on the Internet have not been peer reviewed and you have a recipe set for disaster!
This post is to cater towards the new flyer rather than the advanced flyer. I will not discuss before and after takeoff checklists, how to determine aircraft weights, use of the Control Display Unit (CDU) or how to configure the overhead, but rather instruct on the basic procedures used to takeoff, climb and transition to cruise.
I have attempted to simplify the procedures to avoid confusion.
The first aspect to take on board is that there is no absolute correct method for takeoff and climb. Certainly, there are specific tasks that need to be completed; however, there is an envelope of variability allowed. This variability may relate to how a particular flight crew flies the aircraft, environmental considerations (ice, rain, wind, noise abatement, obstacles, etc.), flight training, or a specific airline policy.
The second point to consider is what CDU software the avionics suite replicates. There are different protocols between FMC U10.6 and FMC U10.8 and these equate to different procedures that should be followed. As at writing, ProSim-AR uses U10.8A.
Whenever variability is injected into a subject you will find those who work in absolutes having difficulty. If you’re the kind of person who likes to know exactly what to do at a particular time, then I’d suggest you find a technique that fits with your liking and personality.
Table 1 is a ‘ready reckoner’ that explains much of what occurs during the takeoff roll, climb out and transition to altitude. Like anything there are some specific terms that you need to remember and more importantly understand.
The information in the below chart has been peer reviewed by B737 Captain. He agreed with the content; however, reiterated the variability allowed by flight crews when flying the B737.
TABLE 1: Condensed points that need to be addressed during a takeoff and climb. The procedures are outlined in more detail below the table. The table does not reflect any particular airline operation and is for reference only.
The following procedures assume other essential elements of pre-flight set-up have been completed.
1. On the Mode Control Panel (MCP) dial into the altitude window an appropriate target altitude, for example 13,000 feet.
2. Command speed is set at V2 using the MCP. Dial into the MCP speed window the V2 speed as indicated in the CDU. The V speed is defined by the CDU based on aircraft weight and several other parameters.
- V2 is the minimum takeoff safety speed and provides at least 30° bank capability for all takeoff flaps.
- An airspeed bug is automatically set 15 knots above command speed. V2+15 knots provides 40° bank capability for all takeoff flaps. The bug can be used to match the correct climb-out speed. The bug indicator disappears at acceleration height (usually 1000 feet ASL).
- A flight crew may fly either +15/20 knots (maximum +25 knots) above V2 command speed to lower/increase pitch during takeoff depending on the weight of the aircraft and other environmental variables. Company policy frequently dictates whether +15/20 knots is added to V2. (this assumes both engines operational).
- Command speed remains set at V2 (in the MCP) until changed by the pilot for acceleration and flap retraction or until a subsequent pitch mode is engaged. Manually select flaps up maneuver speed at acceleration height (1000 feet).
3. Turn on the Flight Director (FD) switches (pilot flying side first).
4. Set flaps 5 and trim the aircraft using the electric trim on the yoke to the correct trim figure for takeoff. This figure is shown on the CDU (for example, 5.5 degrees) and is calculated dependent upon aircraft weight with passengers and fuel. It is usual for the trim figure to place the trim tabs somewhere within the green band.
5. Arm the A/T toggle (the airline Flight Crew Operations Manual (FCOM) may indicate different timings for this procedure).
6. Release the parking brake and advance the throttle levers manually to around 40%N1 (some Flight Crew Training Manuals differ to the %N1 recommended. ie: 60% N1).
- You do not have to stop the aircraft before initiating 40%N1. A rolling takeoff procedure is recommended for setting takeoff thrust as it expedites the takeoff and reduces the risk of foreign object damage or engine surge/stall due to a tailwind or crosswind.
- After thrust has reached 40%N1, wait for it to stablise (roughly 2-3 seconds). Look at the thrust arcs on the EICAS screen to ensure both arcs are stable. Takeoff distance may be adversely affected if the engines aree allowed to stabilize for more than approximately 2 seconds before advancing the thrust levers to takeoff thrust.
7. Once the throttles are stabilized, advance the thrust levers to takeoff thrust or depress one or both TO/GA buttons. If TO/GA is used the thrust levers will automatically advance by the A/T to the correct %N1 output calculated by the Flight Management System.
- Do not push the thrust levers forward of the target %N1 - let the A/T do it (otherwise you will not know if there is a problem with the A/T). See point 10 concerning hand placement.
- Ensure target %N1 is initiated by 60 knots ground speed.
8. Maintain slight forward pressure on the control column to aid in tyre adhesion. Focus on the runway approximately three-quarters in front of the aircraft. This will assist you to maintain visual awareness and keep the aircraft centered on the centerline.
9. During initial takeoff roll, the pilot flying should place their hand on the throttle levers in readiness for a rejected takeoff (RTO). The pilot not flying should place his hand behind the throttle levers. Hand placement facilitates the least physical movement should an RTO be required.
10. The pilot not flying will call out ‘80 Knots’. Pilot flying should slowly release the pressure on the control column so that it is in the neutral position. This will soon be followed by V1 indicated on the speed tape of the Primary Flight Display (PFD). Takeoff is mandatory at V1 and Rejected Takeoff (RTO) is now not possible. The flight crew, to reaffirm this decision, should remove their hands from the throttles; thereby, reinforcing the ‘must fly’ commitment in that the speed is beyond the limits for a safe RTO.
11. At Vr (rotation), pilot not flying calls ‘Rotate’. Pilot flying slowly and purposely initiates a smooth continuous rotation at a rate of no more than 2 to 3 degrees per second to an initial target pitch attitude of 8-10 degrees (15 degree maximum).
- Takeoffs at low thrust setting (low excess energy) will result in a lower initial pitch attitude target to achieve the desired climb speed.
- Normal lift-off attitude for the B737-800 is between 8 and 10 degrees providing 20 inches of tail clearance at flaps 1 and 5. Tail contact will occur at 11 degrees of pitch if still on or near the ground.
- Liftoff attitude is achieved in approximately 3 to 4 seconds depending on airplane weight and thrust setting.
12. After lift-off, continue to raise the nose smoothly at a rate of no more than 2 to 3 degrees per second toward 15 degrees of pitch attitude. The Flight Director (FD) cues will probably indicate around 15 degrees.
- Be aware that the cues provided by the flight director may on occasion be spurious; therefore, learn to see through the cures to the actual aircraft horizon line.
- The flight director pitch command is not used for rotation.
13. You will also need to trim the aircraft to maintain minimum back pressure (neutral stick) on the control column. The B737 is usually trimmed to enable flight with no pressure on the control column. It is normal following rotation to trim down a tad to achieve neutral loading on the control column. Do not trim during rotation.
14. When positive rate has been achieved, and double checked against the speed and vertical speed tape in the PFD, the pilot flying will call ‘Gear Up’ and pilot not flying will raise the gear to minimize drag and allow air speed to increase.
15. The Flight Director will command a pitch to maintain an airspeed of V2 +15/20. Follow the Flight Director (FD) cues, or target a specific vertical speed. The vertical speed will differ widely when following the FD cues as it depends on weight, fuel, derates, etc. If not using the FD cues, try to maintain a target vertical speed (V/S) of ~2500 feet per minute.
- If the FD cues appear to be incorrect, or the pitch appears to be too great, ignore the FD and follow vertical speed guidance.
- Bear in mind that vertical speed has a direct relationship to aircraft weight - if aircraft weight is moderate use reduced takeoff thrust (derates) to achieve recommended vertical speed.
V2+15/20 is the optimum climb speed with takeoff flaps. It results in maximum altitude gain in the shortest distance from takeoff.
16. Fly the Flight Director (FD) pitch bars maintaining airspeed of V2 +15/20. Maintain an air speed of Vr +15/20 until you reach a predefined altitude called the Acceleration Height (AH). AH is defined by company policy and is usually 1000 feet or 1500 feet altitude.
17. At Acceleration Height (usually 1000 feet RA), push the control column forward, increasing air speed and lowering vertical speed. A rough estimate to target is half the takeoff vertical speed. Press N1 on the MCP (if wanted) and follow FD cues to flaps UP speed.
- Note that N1 will automatically be selected at thrust reduction altitude (usually 1500 feet RA).
- When N1 is selected the autothrottle will control the speed of the aircraft to the N1 limit set by the Flight Management System (FMS). Selecting N1 ensures the aircraft has maximum power (climb thrust) in case of a single engine failure.
- N1 mode does not control aircraft speed. The autothrottle will set maximum N1 power. Speed is controlled by aircraft pitch attitude.
- Selecting N1 on the MCP does not provide any form of speed protection.
18. Dial into the MCP speed window the climb speed or constraint speed. Observe the PFD and retract flaps on schedule following the flaps retraction bugs located on the speed tape.
- Do not retract flaps unless the aircraft is accelerating and the airpeed is at, or greater than V2+15/20 - this ensures the speed is within the manoeuvre margin to allow for over-bank protection. Do not retract flaps below 1000 feet RA.
- At Acceleration Height the flaps should be retracted on schedule and if required automation engaged (VNAV. LVL CHG, etc), when the flaps are in the UP position. If noise abatement is necessary flaps retraction may occur at Thrust Reduction Heigh.
- A common prompt (memory jogger) is speed, N1, flaps (see point 17).
19. At flaps UP (marked UP on the PFD speed tape), either manually fly (pitch and roll control) to altitude or engage automation (Level Change, VNAV, LNAV, V/S, CWS, CMD A/B engaged). Remember that unless you select another mode, TOGA command mode will be engaged from takeoff until you each the assigned altitude on the MCP.
- Selecting N1 on the MCP does not disengage TOGA mode (if you want to disengage/cancel TOGA mode prior to reaching 400 feet ASL then both Flight Director switched need to be turned off)
- Some flight crews when reaching acceleration height (AH) call 'Level Change, Set Top Bug'. This ensures that TOGA speed is disengaged (cancelled) and causes the Flight Director (FD) cues to lower; thereby, increasing speed as Level Change increases thrust.
- Other flight crews may engage Control Wheel Steering (CWS) following flaps UP and fly in this mode to 10,000 feet before engaging the autopilot (CMD A/B). Whatever the method, it is at the discretion of the pilot in command and the method is often stipulated by company policy.
- If using automation, VNAV can be engaged no lower than 400 feet RA (company policy may indicate otherwise). Note that selecting VNAV does not provide flaps overspeed protection.
- Engaging VNAV will automatically blank out the MCP speed window and increase the speed of the aircraft to that defined in the CDU (usually 250 KIAS). The speed can be observed in the PFD. Follow the Flight Director (FD) cues.
20. The aircraft is usually flown at a speed no faster than 250 KIAS to 10,000 feet. At 10,000 feet, climb speed is automatically populated if automation (VNAV) was engaged at a lower altitude. The same will occur for cruise speed.
- If the aircraft is being flown by hand (manually), then the appropriate climb and cruise speeds will need to be dialed into the MCP. At 10,000 feet, dial 270 KIAS into the MCP speed window and then at 12,000 feet dial in 290 KIAS. Follow the Flight Director (FD) cues or maintain roughly 2000-2500 fpm vertical speed. At cruise altitude, transition to level flight and select on the MCP speed window 290-310 KIAS or whatever the optimum speed is (see CDU).
The above guidelines are general. Specific airline policy for a particular airline may indicate otherwise. Likewise, there is considerable variation in how to actually fly the B737, and when and what type of automation to engage.
LEFT: Qantas Airways departs Queenstown, New Zealand.
There are also, located within the CDU, several parameters which if altered before takeoff can have a marked effect on aircraft performance.
It is very easy to become confused during the takeoff phase - especially in relation to automation, V speeds and how and when to change from TOGA to MCP speed. The takeoff phase occurs quickly and there is a lot to do and quite a bit to remember - there is little time to consult a manual or cheat sheet.
One way to gain a little extra time during the takeoff transition, is to select an appropriate derate. Apart from being standard practice in the real-world for many takeoffs, a derate will also help control over-pitching and high vertical speeds which are common when the aircraft is light due to minimal fuel loads and cargo.
During the initial takeoff, thrust (%N1) is automatically selected when you engage the TOGA buttons. N1 (%N1) is a measurement in percent of the maximum rpm, where maximum rpm is certified at the rated power output for the engine (most simple explanation). Therefore, 100%N1 is maximum thrust while 0%N1 is no thrust.
At 80 knots the automated system will engage thrust to N1 at a percentage commensurate with the settings set in the CDU (aircraft weights, climb etc.). N1 (TOGA command mode during takeoff) always controls the speed of the aircraft with pitch. To determine what is controlling the thrust of the aircraft, always refer to the Flight Mode Annunciations (FMA) in the PFD.
To enable a quick overview of annunciations during the takeoff refer to Table 2.
After acceleration height has been reached, the nose lowered to increase speed, and flaps retracted; it is at the discretion of the pilot flying (or company policy) to what mode of automation is selected. It is common place to either use Level Change (LVL CHG) or Vertical Navigation (VNAV) and Lateral navigation (LNAV).
Theoretically, a crew can fly the F/D cues at V2+15/20 to the altitude set in the MCP; however, there will be no speed protection available. If the pitch recommendation (Flight Director cues) are not followed, then airspeed may be either above or below the optimal setting.
Unless an alternative mode is selected, the aircraft will remain in TOGA command mode and be controlled by N1 until the altitude set in the MCP is reached. Other modes which will exit the TOGA mode are LVL CHG, VNAV and Vertical Speed (V/S), or you can engage Altitude Hold (ALT HOLD). Engaging the A/P will also disengage TOGA command mode.
It is important to understand what controls which command mode. For example, LVL CHG is controlled by N1 and pitch and in this mode the A/T will use full thrust while the speed will be controlled by pitch.
TABLE 2: PFD and FMA annunciations observed during takeoff and climb.
Various modes provide speed protection with or without flaps extended.
When you select LVL CHG the speed window will open allowing you enter a desired speed. LVL CHG is speed protected meaning that the speed should not precede past your MCP entered speed. The mode, which is controlled by N1, will adjust the pitch of the aircraft to match the desired speed.
VNAV also has speed protection but not with flaps extended. The speed in VNAV is defined by the value (speed) set in the CDU. In contrast, Vertical Speed (V/S) provides no speed protection as it holds a set vertical speed. In V/S, if you are not vigilant, you can easily encounter an over speed or under speed situation. Selecting N1 only on the MCP without any other mode engaged does not provide speed protection and only ensures maximum thrust (as set in the FMS).
It is imperative that you carefully scrutinise the Flight Mode Annunciator (FMA) to ensure you are flying in the correct mode.
The takeoff can be very fast, especially if you have an aircraft which is light in weight (cargo, passengers and fuel).
LEFT: B737 CDU showing Takeoff page. A takeoff can occur without the completion of data; however, some automation features such as VNAV and LNAV will not be available, and V1, V2 and Vr will not be propagated on the speed tape (click to enlarge).
Soon after rotation (Vr), the aircraft will be at acceleration height and beyond… It’s important to remain on top of what is happening and try to think one step ahead of the automated system that is flying the aircraft.
Flight crews typically fly manually at least until all the flaps are retracted and the aircraft is in clean configuration. A command mode is then selected to continue the climb.
If the aircraft is light, flight crews often limit the takeoff thrust by one of several means. Typically, it is by using a thrust derate and selecting either CLB 1 or CLB 2, or entering an assumed temperature thrust reduction - both done in the CDU. Selecting either option will cause a longer takeoff roll, delay the rotation point (Vr) and cause a less aggressive high pitch climb than observed if these variables were not altered.
Reiterating, the above guidelines are generalist only. Flight crews use varying methods to fly the airliner and often the method used, will be chosen based on company policy, crew experience, aircraft weight and other environmental factors, such as runway length, weather and winds.
Additional takeoff information - mainly in relation to acceleration height, thrust reduction height, and derated thrust can be read on these pages.
The two tables in this post can be downloaded in PDF format:
The content in this post has been proof read for accuracy; however, explaining procedures that are convolved and subjective can be challenging. Errors on occasion present themselves. if you observe an error (not a particular airline policy), please contact me so it can rectified.
Acronyms and Glossary
AFDS – Autopilot Flight Director System
AH - Acceleration Height. The altitude above sea level that aircraft’s nose is lowered to gain speed for flap retraction. AH is usually 1000 or 1500 feet and is defined by company policy. In the US acceleration height is usually 800 feet RA.
CDU / FMC – Control Display Unit / Flight Management Computer (term used interchangeably on this website). The visual part of the Flight Management System (FMS)
CLB 1/2 – Climb power
Command Mode – The mode of automation that controls thrust
EICAS – Engine Indicating and Crew Alerting System
F/D – Flight Director (Flight Director cues/crosshairs)
FMA – Flight Mode Annunciation located upper portion of Primary Flight Display (PFD)
KIAS – Knots Indicated Air Speed
LNAV – Lateral Navigation
LVL CHG – Level Change Command Mode
MCP – Mode Control Panel
RTO – Rejected Take Off
T/O Power – Takeoff power
Throttle On & Off-Line – Indicates whether the throttle is being controlled by the A/T system.
TOGA – To Go Around Command Mode
TRA - Thrust Reduction Altitude. The altitude that the engines reduce in power to increase engine longevity. The height is usually 1500 feet; however, the altitude can be altered in CDU
V/S – Vertical Speed Command Mode
V1 – is the Go/No go speed. You must fly after reaching V1 as a rejected take off (RTO) will not stop the aircraft before the runway ends
V2 – Takeoff safety speed. The speed at which the aircraft can safely takeoff with one engine inoperative (Engine Out safe climb speed)
VNAV – Vertical Navigation
Vr – Rotation Speed. This is the speed at which the pilot should begin pulling back on the control column to achieve a nose up pitch rate
Vr+15/20 – Rotation speed plus additional knots (defined by company policy)