What Are Pickle Fork Cracks And Should You Worry About Them?

Just over a month ago we reported on a cracking issue that was discovered on some components found on the Boeing 737 Next Generation (NG) aircraft. The Federal Aviation Administration had issued an order for airlines to inspect their affected jets after the Boeing alerted it to the issue. The component where these cracks occur have the name “pickle forks”. So what are pickle forks on an aircraft and why should you care?

Air Transat will eventually transition to become an all-Airbus fleet. It currently still operates the Boeing 737. Photo: Lord of the Wings via Wikimedia Commons

What is a pickle fork (in aircraft terms)?

Named after the utensil used to pierce and handle pickles, pickle forks are the component that attach the plane’s body to its wing structure. These components help to “manage the stress, torque and aerodynamic forces that bend the connection between the wings and the body of the jet”.

Boeing 737 NG pickle forks
The “pickle forks” as shown in Boeing Patent US9399508B2. Photo: Boeing

According to KOMO News, pickle forks are “designed to last more than 90,000 landings and takeoffs without cracking…and there could be dire results if the system fails”. A former Boeing engineer who asked to remain anonymous tells KOMO that the issue is especially concerning as it was found relatively early in the plane’s service:

“It’s unusual to have a crack in the pickle fork. It’s not designed to crack that way at all. Period.”

Why should you worry about them?

We should emphasize that Boeing and affected airlines are working hard to inspect all affected aircraft and would not fly their 737 NGs if there was a risk to passenger safety.

However, you should at least be aware of the issue if you have travel plans with an airline that has a fleet comprised of these aircraft. This is because replacement of a component like this isn’t necessarily a quick and easy job. In fact, addressing the issue requires grounding for an unspecified amount of time. As such, you may find yourself on a different aircraft or have your schedule changed around.

Qantas-boeing-737-cracks
Qantas has found hairline cracks in the pickle forks of three Boeing 737-800s. Photo: Qantas News Room.

Most recently, Qantas says it has removed the three affected aircraft for repairs while Korean Airlines and other Korean carriers have had a total of nine jets grounded because of the issue. At the beginning of last month, Southwest Airlines revealed two of its aircraft have been identified to have pickle fork cracks.

The carrier, as well as European budget airline Ryanair, could be affected a little more seriously. This is because both airlines operate an all-737 fleet. Southwest’s operations have already been stifled due to the grounding of its 737 MAX.

The full, official statement from Boeing

Responding to a request for comment, a Boeing spokesperson responded with this official statement:

Safety and quality are Boeing’s top priorities. Boeing notified the FAA of this issue and has been actively engaged with our 737NG customers globally in a plan to support the required inspections.

Boeing has provided all 737NG customers detailed instructions for conducting the inspections and reporting the results. The company has held multiple customer engagements to ensure all technical questions are being addressed. Boeing is actively working with customers that have airplanes in their fleets with inspection findings to develop a repair plan, and to provide parts and technical support as necessary.

Boeing regrets the impact this issue is having on our 737NG customers worldwide and we are working around the clock to provide the support needed to return all airplanes to service as soon as possible. This issue does not affect any 737 MAX airplanes or the P-8.

Just over 1,000 airplanes have reached the inspection threshold, with less than 5 percent having findings that will need repair. However, we are not providing a list of customers impacted.

Boeing 737 MAX
Boeing assembles its 737s in Renton, Washington. Photo: Boeing

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David G

Do airliners come with a warranty, like a car? If a safety issue is found, even after some years, is the manufacturer liable for the repair cost? I’m thinking of the worldwide airbag recall on cars over the past few years where the fix has been performed free, many years after the warranty has elapsed.

Peter

I don’t know if planes come with an official warranty, but you can be sure that the airlines will slap these costs on Boeing…if necessary, via lawsuits.
I read elsewhere that replacing affected pickle forks costs $250.000 per plane!

Henning

Of course we should be worried, they hold the fuselage to the wings.

Bernie

Let’s not worry everyone too much, pickle forks are a modification that strengthens the wing attachment. They do not, alone, hold the wings to the fuselage.

Peter

The pickle forks are the main load bearing connections between the wings and fuselage, and they have to deal with forces generated by static loads (fuel in the wings) and dynamic loads (wing movement during turbulence / roll). As such, they are a critical component in the construction.

The fact that they are cracked is evidence that the forces involved are too much for them. If they severed altogether, the consequences would probably be dire.

Norman

I would like to know if this is a result of bad design or bad manufacture. Any insight , Chris?

Peter

Norman, Boeing are currently trying to find out whether all the cracked pickled forks in question come from a given batch (situation A) or from various batches (situation B).
– In situation A (best case for Boeing), the problems are probably caused by a manufacturing error, e.g. impure metal, wrong tempering process, wrong casting temperature, etc.
– In situation B (worst case for Boeing), the problem is an underlying mechanical shortcoming in the design.
The FAA will hopefully provide more information in due course.

Bernie

The forks that have been “pickled” are probably those in need of an inspection. 😀

Moaz Abid

There are always faults in using newly next generation technology, pretty much like driverless cars. Uber had an accident killing a pedestrian using a driverless car in USA. The best thing is to learn from those mistakes and improve them. Good Luck Boeing.

Chris

How many 737 NG have been built ?
And does Ryanair have started the inspection of their 737 ?

Peter

– Just over 7000 NGs have been delivered. – The FAA airworthiness directive (currently) only requires inspection of aircraft with more than 22600 cycles (=take off / landing pairs). I don’t know if any Ryanair planes fit into that category…I doubt that there would be many, because Ryanair has a relatively young fleet. Some airlines (Qantas, Southwest) have also voluntarily started checking aircraft with fewer cycles, but I don’t know if Ryanair plans to do that. On a separate (but related) note: Ryanair is already very publicly angry with Boeing as a result of the MAX fiasco. Now that there’s… Read more »

Why Soitanly

To the Boeing Company: The U.S. Supreme Court has ruled that corporations are people. Congress can impute to a corporation the commission of certain criminal offenses and subject it to criminal prosecution therefor. In actions for tort, a corporation may be held responsible for damages for the acts of its agent within the scope of his employment, even if done wantonly, recklessly or against the express orders of the principal. While corporations cannot commit some crimes, they can commit crimes which consist in purposely doing things prohibited by statute, and in such case they can be charged with knowledge of… Read more »

MAK

what a disaster for Boeing – MAX + NG! upto 2018 there were 6300+ 737NGs in service – 5% having cracks = 300+ aircraft – flying the newest versions of 737s has become a matter of flying on ‘a wing & a prayer’. An early failure surely points to ‘problems’ in the material used; or some form of ‘overloading’ the structure?

Peter

It could potentially be the material. But it could also be that the fork is too thin, for example, or has a sub-optimal shape.

I’m not sure if the forks in the 737 NG are the same design as in the older 737 Classic. If they are, then that would potentially be a major blunder by Boeing, because the wings on the 737 NG almost certainly have to bear greater loads than in the Classic (just look at the difference in engine size, for example).

john

“Safety and quality are Boeing’s top priorities.” Sure thing Boeing. We trust you. (sarcasm in case you missed it)

Azman Shah

Dont you tell me we hadnt learnt from the 737 max incidents. Even a hairline cracks its should be rectified Asap. Its to late if the cracks get serious during the flight. Dont you worry about the life of more than 200 people on board?