When a Wing Comes Apart
February 26, 2024
SO, LAST WEEK, a passenger videoed a damaged wing slat on a United Airlines flight headed from Denver to Boston. Learning of the problem, the crew conferred with its dispatch and maintenance team, and a decision was made to divert the Boeing 757 into Denver.
Copyright issues prevent me from re-posting videos or images, but you can easily Google it. The upper part of the slat, along the front of the wing, inboard of the right engine, appears shredded and chewed. it’s a composite material, and somehow it delaminated and fragmented. How, exactly, is unknown.
Well, no surprise, the pictures are all over media and social media — so much as those things are different nowadays — accompanied by a barrage of terrifying headlines: “Passenger Sees Wing Coming Apart.” “Passenger Horror as Wing Comes Apart.” And so on.
The wing, in fact, did not come part. What “came apart,” if we can call it that, is a portion of a slat. There are several slats per wing, sectioned along the leading edge. Like the trailing-edge flaps along the back of the wing, these devices are deployed in stages to increase lift at low speeds. You’ll see them extended during takeoff and landing, then retracted during cruise.
It’s a terrible look for sure, but the danger here was minimal. One small hazard might’ve been broken material striking the rear stabilizers. Worst case would’ve been the slat breaking apart further, or detaching completely, unlikely as that might be, but even this wouldn’t crash the plane, so long as the stabilizers or tail weren’t struck and badly damaged.
There may have been a discussion about whether or not to deploy the slats for landing. There’s no way to isolate a specific slat, so keeping the broken one retracted would’ve meant a “no flap landing,” where all of the high-lift devices, both flaps and slats, remain stowed. A jetliner can land just fine this way — it just needs to do so at a higher speed, requiring more runway.
A few months ago, due to a malfunction, a 757 I was piloting made a no-flap landing in Colombia. We came in fast, as our checklists dictated (I can’t recall the exact speed), and used about two-thirds of the runway, as our calculations told us to expect. But otherwise the landing was routine. In most ways, what happened to me was more serious than what the United pilots had to deal with, just not as photogenic and so it got no attention.
As it happened, the United pilots deployed the slats and flaps as they normally would, and the plane landed safely. To nobody’s surprise. Certainly not mine.
Segmented slats line the leading edge of a wing, shown here fully retracted. They are operated hydraulically.
I suspect the choice to divert was a practical one as much as anything. Denver is one of United’s biggest hubs, and the plane would need lengthy repairs; grounding it in Boston was going to trigger a cascade of logistical complications affecting hundreds of passengers. In Denver, an airplane swap could be handled expeditiously, with all the needed maintenance resources on site.
Nothing to fret about, all in all. But if the viewer comments on various media sites are any indication, the public is alarmed. “What’s going on in the skies these days?” Asks one reader, his sentiments echoing those of others. “Yet another close call.”
Not really. What’s actually happening is a matter of exposure. These sorts of minor incidents have always been with us. What’s different is the media environment in which they’re occurring. In the old days you never heard about them. Today, everything is photographed and everything is shared. The smallest mishap is on Instagram and other platforms within minutes, visible to millions. A landing gear problem; a compressor stall; a pressurization malfunction. The sky is falling.
Except it’s not. As I’ve talked about in prior articles, major airline disasters are far, far more uncommon today than they used to be. A dearth of them has led to us putting undue focus on relatively harmless incidents instead.
I’m unsure which is more to blame, social media or actual news sources. They seem to feed off one another, so maybe it’s a moot point.
The fact that the 757 is a Boeing model has only made things worse. Thanks to the controversies surrounding the 737 MAX, anything involving a Boeing jet now gets extra scrutiny, deserved or not. No matter that the 757 is a 42 year-old design with an excellent safety record. The B-word is what counts.
Let’s face it, everyone is looking for attention, for views and hits, be it FOX News or the Times or a 16 year-old Instagrammer. Few things, meanwhile, garner more attention or stoke more fear than plane crashes. The mere suggestion of one, realistic or not, is an automatic go-to for eyeballs. And so, here we are.
For more about slats, flaps, and the other doodads than help a plane fly, see chapter one of Cockpit Confidential.
Related Stories:
LUCKY AND GOOD
TWENTY YEARS AND COUNTING
Photos by Asato Hisada, courtesy of Unsplash.
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35 Responses to “When a Wing Comes Apart”
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Patrick,
When one door closes, another opens. – Boeing
Patrick,
Great blog. I thought of this post, which I read a few days ago, again today. I agree about the mass hysteria media-wise. But UA had a not-so-great week – losing a tire at SFO on takeoff, an engine fire 15-minutes after takeoff, and landing gear failure in HOU. Yikes.
Patrick,
Thanks for the answer on no flap landing, I found it quite interesting. Also, I now know there are two different spellings of “Columbia” and “ Colombia”
More concerning is a report out today of an incident in which the rudder pedals were stuck on a United 737 Max 8 upon landing at Newark. A test flight of the aircraft three days afterwards duplicated the issue. This, especially if not limited to this particular aircraft, is a very serious safety issue to say the least.
https://www.reuters.com/business/aerospace-defense/us-ntsb-probes-stuck-rudder-pedal-issue-boeing-737-max-flight-2024-03-07/
I just read that, on March 4th, there was an engine failure on a United 757-300 enroute from HNL to SFO. The incident occurred late in the flight, within a couple hundred miles of the destination airport, and the aircraft completed the flight normally – but, of course, it was a Boeing, so… Adding insult to injury on the Microsoft News website was a glaring error in the story that the 757 “had only been in service for two weeks.”
Ted Kenney
You were very lucky to have survived,
A leading edge slat segment that is damaged or missing can be very dangerous. Under those circumstances, the L and R wings have different maximum lift hence different stall speeds. If the airplane slows into that speed gap, one wing will stall. The asymmetric lift will cause the airplane to roll suddenly, perhaps out of control. The only remedy is to accelerate so that lift once again becomes symmetric. (There will be a slight lateral mistrim due to asymmetric wing drag)
Chris H
Leading edge flaps give more lift at the same speed (raise the lift curve); trailing edge flaps reduce stall speed by increasing lift beyond the flaps up maximum (extend the lift curve).
They MUST be used together,
Leading and trailing edge high-lift devices are controlled from a single lever. On some aircraft, the first detent will extend partial leading edge flaps; the second detent will extend the full leading edges. On other aircraft, all leading edge devices extend with the first detent.
Trailing edge flap extension increases with further detents without any additional leading edge motion.
As ever the voice of reason. Thanks for this. For future reference, you can include links to articles and videos on other sites. Doing so does not infringe on any IP, copyrights included.
What’s your take on the Boeing fiasco. Beside the Max crashes, and the door plugs, we see other stories, such as cracked windshield, construction debris left on board,and so on.
Before the merger with McDonald-Douglas, Boeing was a fabulous company, with an equally fabulous history. Since the merger, it’s profit and speed above all.
It’s almost like the planes are being made by Lego, or Fisher-Price.
Ah, yes, of course. I did make a mistake regarding the airline involved. And did that make any difference to the crew and passengers, of just those several situations? They died simply because of a (or several) maintenance personnel and probably corporate executives and the FAA not being honest. Please, let’s stay on point and look at what really is the cause of so many aviation disasters. Shortsightedness, complacency, not following established procedures in our piloting and maintenance activities needs to be addressed – not squawking about a mistake of an airline name. Have you researched the cause of any of those disasters? Hmmmm . . .
Exactly my thoughts on Boeing! United has been the maintenance for this plane the last 42 years!!
while you may be comfortable there is a cycle to everything esp as it pertains to execution of quality repair and maint in economies where hiring is questionable and training non-existent as well QA checks of same. Being in the commercial nuclear industry we see many times where time rush and lack of quality workmanship just about makes for a “very bad nuclear day like within a 10 mile radius. 🙂
And with my luck I am sure I would be on that plane that say, someone didnt torque the bolt quite right or mis mixed the epoxy, etc. Just my .02$
With 36 years with a major airline and 27,000 hours, I am surprised that I have not run across the works of Patrick Smith. Perhaps it is because I am from a different generation, but I really identified with his comments on the wing slat incident, as they were right on target. I too have PIC time in many Boeing aircraft starting with the 707, 727, 747 and 757/767 up to retirement in 2001. To applaud engine manufacturer Pratt and Whitney, I would like to point out that with my 7,000 hours in the 707 I only had one engine shut down, which represents 28,000 hours engine time. Truly amazing.
In those years I too do not recall such airline scrutiny over any minor incident, perhaps because the passenger demeanor was different. Today I am disgusted about media coverage of current incidents, such as two aircraft clipping wings on the taxiway, with no injuries to the pax, as well as the wing slat event. I’m sorry that my favorite aircraft manufacturer is under the gun, but I guess times have changed.
John Pappas: For all your many years of experience, you shoud refresh your research skills. Southwest has never operated the MD-80. That was an Alaska Airlines flight that ended in the Pacific.
I have no idea as to the cause of the slat failure nor this author’s situation in the 757 that he was flying. Yes, things do happen but currently we have and continue to have a spate of ‘maintenance’ malfeasance. Probably has happened since O & W first flew but it seems like it has become close to an everyday event. I personally know of a UPS aviation mechanic who falsified critical documents regarding work not done while he was ‘moonlighting’. This was reported to the FAA and UPS which did absolutely nothing. To my knowledge UPS continues to employe this person as an A&P mechanic. Unless and until the FAA and industry executives stop the coddling of known, proven errant pilots and mechanics nothing will change. Mechanic malfeasance is quite simply a quiet killer – mostly hidden until a disaster happens, nee American Airlines DC-10 Chicago, Southwest Airlines MD-80 jackscrew, Japan Airlines pressure bulkhead – the list could go on and on – with hundreds if not thousands DEAD! And NO, the problem is not simply the current state of communication thru social or mainstream media – the public is rightly concerned. The problem lies with corporate management and the FAA not being responsible and taking action to keep the public safe. And yes, I have been heavily involved with aviation for many, many years – ATP, A&P, numerous Type Ratings, WBMPA, JD, Piper cubs to supersonic fighters.
> that bottom line engineering design, production and maintenance is the rule, not the exception
> the current “B” is not the “B” of yesteryears and deserves the intense attention.
I’m not sure WTF “the current “B”” is supposed to mean in this ramble, but I will point out the 757 first flew commercially in 1983. That’s, yes, 41 years ago. If you have a point, that point isn’t supported by your arguments.
I am happy to step aboard a 757 and take my cattle class seat. Magnificent airplane, with or without one delaminated slat. Recent Boeings, not so much.
Yes, much ado about not much. I flew the Bombardier CRJ twinjet in it’s many versions and have performed a fair number of flap/slat failure arrivals. It’s a bit exciting for the pilots as the usual sight-picture from the flight-deck is quite different from the norm … and everything happens faster. The most interesting was the pitch on the flaps-fail-up/slats-out approach and landing attitude: high! Indicated approach speeds, if I recall, generally added 30-40 kts to normal ref.speed, depending on landing weight. In the referenced 757 incident, it looks like the composite trailing edge of the slat shredded itself, but the metal leading edge and slat structure were quite intact. Well handled!
Response to Chris H: As I remember, and it was a long time ago, the L-1011 (and probably most other airliners) had separate circuit breakers for the slats and flaps. The pilots could have pulled the slats CB and still extended the flaps. Or just landed with no slats nor flaps.
When taking a night catapult launch from the deck of the USS Ranger in 1967 my starboard leading edge slat fell off. Since the A3 skywarrior tends to stall at 180 knots with a retracted or missing slat and the . catlaunch speed is 165 kenots things immediately became somewhat dicey. Violent stall occurred on the right wing accompanied with a lot of shutters and some loss of altitude. I was able to recover just prior to hitting the water and climbed up to 10,000ft. Ranger called me to see if I had lost a slat and ofcouse I answered yes. Since my approach speed for carrier landing was 135 kts and my stall speed was 180kts, I elected to divert to Cubi Point with an 8000ft runway. I landed at 200kt and engaged the arresting gear.
You are dead on. I am so sick of the news making a crisis out of every single aviation incident. Save it for the ones that count.
Well said. Yet another case of the ‘echo chamber’ effect of the world’s so-called news causing overreactions.
I just Googled this to see for myself what happened. What was hilarious and a bit disconcerting at the same time was some of the headlines of related articles! My favorite one was from Boston 25 News: “Wing Was Destroyed”. a pure case of the media sensationalizing something that posed little threat to the flight and its passengers. It borders on criminal! I think anyone who flies commercially should have a little bit of knowledge into how an airliner works.
An interesting take on the “Its all good until its not”. Yes crashes due garner lots of attention as they, well, kill up to hundreds of people. Perhaps a ho-hum event to pilots but not to passengers. Looking out your window, trapped in a cylindrical tube, thousands of feet in the air, flown by two strangers, a passenger might get quite disturbed by seeing parts that appear to be deteriorating. Given the millions of cameras in the air daily, its obviously not a common event. I’d rather have the attention as it is constantly being shown that bottom line engineering design, production and maintenance is the rule, not the exception. Publicity is one of the few tools a passenger to influence regulators, airframers and even pilots to say we want safe planes. These are not old cars that can have missing and broken parts but get flown because a pilot can always be found who will fly it. And yes, the current “B” is not the “B” of yesteryears and deserves the intense attention.
The higher elevation would result in a higher landing speed due to higher altitude. That said, I’d take Denver in a heartbeat with long runways like that
> Allan L: Wouldn’t Denver be a suboptimal choice for a no-flaps landing, because of the elevation of the field?”
No. DIA has the longest runway in north america, at 16k feet. That is… immense. And FWIW, as mentioned in TFA, they did a regular flaps/slats landing. Also mentioned in TFA, is that a no-flaps landing just means you need more roll space.
Plus any civilian transport wishing to operate in the US is going to have to be capable of no-flaps (which includes no slats) landings.
Yep, agreed. The eyeball test says that delaminated slat would cause maybe 2% extra drag on that side, and the plane’s automated systems would compensate. Unlikely the pilots would even notice any unusual handling characteristics and would not know about it until back at the terminal, if the pax hadn’t raised concerns.
Nothingburger.
The hype that resulted when this story first appeared in social media is basically another variation of the old “airplanes are being held together by duct tape” nonsense. Even the so-called “mainstream” media — who are supposedly in business to inform and educate — can’t be bothered explaining how modern aircraft are constructed and maintained. Instead, they’d rather trash the reputations and intentions of airlines, flight crews and aircraft manufacturers. As always, thanks for being a light in the darkness, Patrick.
good summary….saw pictures online and the attention seeking posts and news reports were far worse than the damage or risk.
Are the slats and flaps extended with the same control? Or can they be extended independently of each other? Could the plane have landed with flaps extended but the slats not, or is there an aerodynamic reason not to do this?
Wouldn’t Denver be a suboptimal choice for a no-flaps landing, because of the elevation of the field?”
The elevation at DEN means that your true airspeed and groundspeed will be high, yes. But, the airport’s unusually long runways compensate for this.
My own no-flap landing was in Bogota, which is about 3,000 feet HIGHER than Denver. El Dorado’s runways are 12,000 feet long
“757 ..lnded as proscribed>” errr . not a banned landing? PrEscribed likely though
Embarrassing mistake. Fixed.
Another near disaster averted! It didn’t look pretty, but the damaged 757 slat looked fairly functional. Back in 1995, I was flying on an LTU L-1011 from SFO-DUS. As we landed, and the speed brakes popped up, I saw about a 2 square foot section of speed tape peel off the flap’s leading edge. This was in the days before easy access to digital video, so there was no opportunity to record the drama. I told a cabin attendant that some tape peeled off the flaps near the #1 engine and he said he would mention it to the captain. End of story.
Right on Patrick, I have have nothing interesting to add but I’m curious about your no flap landing-how much extra speed did you need to add? And was it in Columbia as in Bogota or South Carolina? The later is over 8,000 feet altitude which I assume would increase the needed speed even more? Do you have data/charts on this (I guess you do) giving landing speed by altitude for no flap landing?
Kevin, for starters don’t mix up Colombia and Columbia.
My no-flap landing was in Bogota, Colombia, which as you note sits at around 8,000 feet elevation. I don’t remember what the speed additive was, exactly, but I remember that our groundspeed over the threshold was close to 190 knots. Still we came to a stop with plenty of pavement remaining, and the brakes stayed remarkably cool.
We were in contact with our dispatcher and maintenace team the whole time, and they backed up up on the number-crunching. This was in a 757. Had it been a 767, or had the runway been wet, we might have diverted.