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Your Flaps Just Failed In Icing Conditions. Now What?

Live from the Flight Deck

You're flying an instrument approach to minimums through icing conditions and as you bring the flaps down, you get a "flap fail" warning message. What are you going to do?

The Scenario

The following scenario is based on a report made by a crew operating a jet in the Northeast through winter conditions. This is a difficult situation. How would you handle it?

On an ILS approach with visibility and ceilings right at minimums, you receive a "flaps fail" warning message on the EICAS just before the final approach fix. You're in icing conditions and immediately perform a missed approach to sort out the issue.

As you perform the missed approach, you notice the airplane rolling and yawing unusually. It's clear that you have failed, asymmetric flaps. One of the first items on your emergency procedures checklist is to "exit icing conditions immediately." Once you finish the checklist, you have to make a decision. Will you divert, or will you restart the approach? You'll have to re-enter the clouds and fly through icing conditions all the way to minimums because of the low weather. If you divert, you'll be low on fuel, because the diversion fuel that's included in your flight plan was only good for a "normal drag" situation. With flaps out, you'll be burning significantly more fuel.

This may sound like a "perfect storm" of events, but it's exactly what happened to one crew right around this time last winter. What are you going to do?

Flying With Asymmetric Flaps

An asymmetric, or split, flap condition happens when one flap deploys or retracts while the other remains in place. If you don't have advanced flap indications, you'll first notice an asymmetric flap deployment when there's a pronounced roll toward the wing with the least flap deflection.

This happens because the wing with the most flap deflection is producing a substantially higher amount of lift. At the same time, increased drag on the flaps-down side creates a pronounced adverse yaw situation, with the nose swinging toward the wing with the most flaps deflected.

Ice Building Up On The Airframe

When ice accumulates on your plane, large increases in parasite drag dramatically reduce your aircraft's performance. On the leading edge of the wing, icing causes the boundary layer to separate earlier. The separation in airflow reduces lift, and increases your stall speed.

If your anti/de-icing system is working properly, the leading edge will stay clean of contamination. However, the leading edge of the flaps will become contaminated during prolonged flight in icing conditions. In addition to that, in an assymetric flap situation, increased yaw and aileron deflection could futher increase ice accumulation on your airframe.

More Drag = Higher Fuel Burn

When you extend the flaps on your plane, you lower your aircraft's stall speed, and at the same time, increase drag. This all happens because extending flaps increases the camber, or curvature, of your wing. When your wing has a higher camber, it also has a higher lift coefficient, meaning it can produce more lift at a given angle-of-attack.

As they say, "nothing in life is free", and the same goes for lift. When you produce more lift, you produce more induced drag. That increase in drag is useful during normal approaches and landings, but if you have to divert with failed flaps (in the down position), you'll suddenly become a test pilot.

To maintain airspeed in cruise with the flaps out, you'll have to fly with a higher power setting and burn a lot of fuel. On top of that, you can't fly faster than Vfe, which in most aircraft is significantly slower than normal cruise speed.

This fuel burn situation is not something you can find in your POH, so you'll have to keep a close eye on how much fuel you're burning per hour.

Flying The Final Approach

With increased ice accumulation, you'll need to be prepared for higher power requirements, higher approach speeds, and a longer landing roll.

What about the asymmetric flaps? At reduced airspeed on final approach, you'll need to use ailerons to maintain wings-level flight.

As airflow decreases during landing, your controls will lose their effectiveness. Because of this, you may need to fly a slightly faster-than-normal approach speed through landing.

As you approach your round out and flare, don't let airspeed dissipate to the point where a cross-controlled stall or a loss of roll authority could happen. Fly the airplane onto the runway with an airspeed that's a safe margin above flaps-up landing speed. And as always, make sure to follow any POH procedures for your airplane.

What Would You Do?

Running out of fuel is your biggest risk during a diversion with a flap failure (in the down position). Airframe icing is a secondary threat and should be taken seriously as well.

What would you do in a situation like this? Fly the approach through the ice, or divert? Tell us in the comments below.

Swayne Martin

Swayne is an editor at Boldmethod, certified flight instructor, and an Embraer 145 First Officer for a regional airline. He graduated as an aviation major from the University of North Dakota in 2018, holds a PIC Type Rating for Cessna Citation Jets (CE-525), and is a former pilot for Mokulele Airlines. He's the author of articles, quizzes and lists on Boldmethod every week. You can reach Swayne at, and follow his flying adventures on his YouTube Channel.

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