Why retract flaps at go-around?

Question

As I understand the procedure for go-around it includes retracting the flaps.

Why is this?

The decision to make a go-around must sometimes be made quickly, under stressful conditions, like in bad weather. Retracting flaps introduces one more thing to do under sometimes stressful conditions.

Speed is low during landing and by retracting flaps you give away safety margin for lift. (Speed may also slow further since the nose is raised during go-around.)

Retracting flaps may also affect pitch and thereby make control of the aircraft slightly more difficult in a situation which may already be stressful.

Answer 1

For the same reason that you don't takeoff with full flaps. Because the climb performance sucks.

Flaps do add lift, but also a lot of drag. A low flap setting often provides more lift than drag, assisting climbout, whereas full flap offers a whole lot of drag, which is desirable when you want to be slow for landing.

But a go-around necessitates gaining height quickly, which will not work with landing flap selected. The usual procedure, at least in light aircraft, is to wait until the vertical speed is neutral or positive before retracting flap. This minimises some of the risks you've raised about aircraft control.

It is often said that a go-around is a period of heavy workload, and managing the flaps and airspeed is not easy. That is why the go-around is a fundamental procedure taught right from the very beginning, and practiced and tested regularly.

Answer 2

You correctly point out some of the challenges surrounding the procedure of retracting flaps upon go-around. Go arounds can be a stressful situation, flaps do give additional lift and margin against a stall, and retracting them does result in a pitch change for which the pilot must compensate. Allow me to address each of these concerns in turn.

1. A go-around can be a stressful situation—especially, as you point out, if additional concerns such as weather come into play. Outside of the training environment, a go around is usually executed because some aspect of the landing is not right, whether that be the pilot, the airplane, the weather, the runway, other traffic, or any combination of those or numerous other conditions. All of these can add up to create a very demanding situation indeed. For this reason, the go-around procedure is carefully taught and practiced often in primary training, and pilots continue to practice and demonstrate it throughout their career. Now, raising the flaps is a normal configuration change that experienced pilots are used to making. Even in demanding situations, raising the flaps should not make an excessive demand on the pilot's attention. This includes already demanding situations such as during a go-around.

2. Airspeed is a major consideration during go-around. Flaps do give additional margin above the stall, some designs more than others. A go-around is all about transitioning from the low-speed approach to the generally higher speed climb out. Thus, the aircraft will be accelerated, typically to the best rate of climb speed (Vy). Typical go-around procedure will call for retracting the flaps once the aircraft is stabilized with sufficient speed, thus reducing—if not eliminating—the risk associated with reduced margin above stall. Even then, the flaps should typically be retracted slowly and in stages, allowing for the speed to increase appropriately. Putting all this together, proper flap retraction during a go-around will not result in excessive risk exposure due to airspeed consideration.

3. Retracting the flaps does result in a pitch change, though different types of flap designs will result in different amounts of change at different rates. Again, the pilot should be experienced and practiced in compensating for this change. Again, since the flaps will typically be retracted slowly and/or in stages, the pilot will be able to compensate throughout the retraction process. During the go-around, the pilot is already making numerous pitch changes and compensations as power, airspeed, and lift change; compensating for flap induced pitch change is part of the expected process.

Now, your question was why should we retract the flaps during a go-around. I have addressed your valid concerns above. Now allow me to give a some reasons why retracting the flaps is advisable or necessary.

1. Flaps reduce climb rate. Flaps add drag which is a good thing for landing, but not good for the climb. In retracting the flaps, the aircraft is configured for its best possible climb performance. Some aircraft have such limited performance that they simply will not climb with full flaps, even at typical elevations and in typical weather. At high elevations and in hot weather, most aircraft will have substantially diminished ability to climb with full flaps.

2. Each type of aircraft has a speed limit for how fast the aircraft is allowed to go with flaps extended (Vfe). This is for structural considerations so that the flaps and wings are not damaged by excessive speed. Retracting the flaps allows for acceleration to climb speed and above without the risk of overspeed damage to the flaps. It is very possible, in some aircraft, to overspeed the flaps after the go-around if they are not retracted soon enough.

3. For multi-engine aircraft, having the flaps retracted typically puts the aircraft in the best configuration to handle an engine failure emergency. If one of the engines fail, the aircraft will climb best on the power of the remaining engine(s) with the flaps retracted.

Answer 3

Since the first objective of any go-around is to establish a stable climb-out, the procedures involved all revolve around changing the current configuration to the required climb-out configuration. Stuff like power-up is pretty obvious in powered aircraft, and since most aircraft use far more flaps for landing configuration then take off, selecting take-off flaps also begins to seem more obvious.

The original question is based on an incomplete understanding about how flaps work, which some of the other answers here have not helped clarify. Most people know that flaps affect lift, drag and attitude, but tend to forget that each is affected by airspeed at different rates. In particular, drag increases far faster then lift when airspeed increases and this is why most aircraft use far more flaps for landing then for take-off. Also people tend to often forget that flaps are used during take-off to reduce the runway requirements, not to increase climb rate, and in a go-around, you are not on the runway so it is not a factor.

Answer 4

Retracting flaps on a go around is not done until a positive climb rate is attained. And even then it should be done incrementally as airspeed picks up. The specific checklist varies among planes, but generally speaking you throttle up, remove carb heat, attain a positive climb rate, (raise landing gear if it is retractable), remove one click of flaps, wait for speed to increase, remove more flaps, wait for speed increase, rinse and repeat...

A go around isn't unlike a takeoff, you want to be climbing as fast as possible, shedding the drag caused by the flaps allows you to pick up speed faster, resulting in a safer climb. But, you can't just fully retract the flaps immediately because they are providing significant lift, you could slam into the ground if you aren't climbing or if you reduce flaps too quickly. There is also the danger of stalling if you reduce flaps before your speed has picked up sufficiently.

Answer 5

First of all, if you fly faster than a stipulated speed with flaps deployed it can damage the flaps, so just in the interest of getting the airspeed up alone, you usually need to retract the flaps as soon as possible.

Flaps are kind of like brakes, they slow the plane down. Not a good thing when you are trying to get to altitude.

Answer 6

Flaps change the wing properties and thereby changes the lift, the approach attitude and lowers the stall speed (all landings are basically controlled stalls). If you need to get out of trouble quickly in a go-around then you may need all the energy that you can get, retracting the flaps changes the wing back to the efficiency of take off to allow you to climb out of trouble.