r/aviation • u/climb-a-waterfall • 11h ago
Question Is it common for aircraft to have a higher takeoff weight than max landing weight?
Why? What is the main limitation on how heavy an aircraft can be at landing?
238
u/Lush_Linguistic 11h ago
Everyone here seems to have missed the simple point that fuel burn means there is essentially zero requirement to land at max takeoff weight barring an emergency
45
u/trying_to_adult_here 7h ago
And (passenger jets at least) are also designed to be able to land safely at max takeoff weight even though that’s above max landing weight. If you lose an engine on takeoff you’re not holding to burn or dump fuel, you’re landing as soon as possible.
Narrowbody Airbus don’t even need an inspection after an overweight landing as long as the crew keeps the sink rate low, and last time I had a 737 land overweight the inspection took less than an hour. The planes are built to land fine heavy, just not every day.
19
u/RealPutin Bizjets and Engines 7h ago
Was looking for this.
When you do gear designs, loads, fatigue analysis, etc you expect a particular distribution of sink rates and weights during landing.
The certification, structural design, safety factors, maintenance programs, etc all are based on that. The occasional overweight or hard landing is expected and engineered for. We know what parts might break or stress at a particular weight/sink rate, we can inspect them. It's really only a problem for an extra hard landing or repeated hard landings
5
u/trying_to_adult_here 5h ago edited 5h ago
I’m a dispatcher so I plan and monitor flights and help the crew with decision-making in emergencies, including participating in radio conferences where the crew and I talk with company maintenance control about whether they recommend continuing to destination or diverting but I’m not actually sure of the specific design loads the plane is engineered for. But it’s pretty common for the crews to be very concerned about overweight landings and for maintenance control to reassure them that it’s fine, and when it’s an Airbus they remind them to stay under the sink rate. I’ve definitely had to talk pilots out of holding for hours to avoid an overweight landing when they’re fueled for long flights on aircraft that can’t dump fuel. Generally if the issue is serious enough that we need to return to field it’s serious enough to justify landing overweight.
I think the magic number for sink rate for the Airbus is 300 feet per minute but I could be misremembering. It’s basically don’t land hard while you’re landing overweight. If there’s any doubt maintenance can pull the recordings from the plane’s onboard maintenance computers, and the Airbus sends them a lot of info automatically. Haven’t had an Airbus land overweight in a few months, my most recent flight to land overweight was a 737 with a medical emergency onboard and they were back in the air within 90 minutes, which included time to take off the ill pax, overweight landing inspection by contract maintenance, placing the used medical supplies and oxygen bottles on MEL, and refueling.
Edit: maybe you were telling not asking. Oh well
1
u/donkeykink420 2h ago
As a non engineer, is it simply put just not certified for higher loads even if it's engineered for them? Ie the certified weights and sinkrate is put at a point where a gear will last for a long time even if there's a rougher landing here and there, but the actual engineering is done so it can survive a hard landing at MTOW without endangering people's lives, and then maintenance is simply accepted? How is that decision even made, figure out how strong it has to be at a minimum to last and then make it a certain amount stronger within a weight restriction? I'm sure it's vastly more complex but I'm genuinley curious
1
u/praetor450 6h ago
You don’t always need to land as soon as possible. Can you hold and burn off fuel to reduce landing weight? Sure
Do you always have to burn off fuel? NoHowever, there are circumstances that would make it better for you to burn off some fuel to reduce the weight. It isnt always necessary to land right away.
If you think you have time then yeah, use the time to set yourself up but an engine failure (depending on the reason) doesn’t mean you need to land asap.
As far as not needing an inspection after landing, I have never flown Airbus so that’s a new to me, but every other type I have flown an overweight landing requires an overweight inspection after the fact. Depending on the actual weight and G loading, that will dictate the extent of the inspection.
15
u/SecureThruObscure 9h ago
Because most of the people here aren’t pilots and haven’t done anything resembling a flight class or flight planning, they just upvote what sounds good.
We live in a world where the fact an LLM can’t plan properly (because it can’t think) has a feedback loop to social media, where social media doesn’t know anything because they copy and paste shit from an LLM.
This shit unironically makes me wish for name verification on the internet.
4
u/BadahBingBadahBoom 9h ago
there is essentially zero requirement to land at max takeoff weight barring an emergency
Would just add in relation to OP's question that whilst maximum rated landing weight is much lower than maximum take-off weight, the landing gears nevertheless need to be rated to not completely collapse if, as you say in an emergency, the aircraft is required to immediately land at its rated maximum take-off weight.
Those landing gears might not be safe to use again after but they sure as hell need to survive at least one heavy landing for the aircraft to be certified. So in a way, yes aircraft are rated to land at the same weight as their maximum take-off weight.
-60
-84
u/_ferko 10h ago
And you that not all aircraft burn fuel.
30
u/pattern_altitude 10h ago
What? Aircraft that don’t burn fuel (very limited subset) account for that in their MTOW/MLW. You’re bringing up something irrelevant in an attempt to feel smart and you seem like an ass.
43
u/KCPilot17 11h ago
Almost always, not just common.
Touching down is the main limitation.
3
u/RyzOnReddit 7h ago
Anything bigger than a small trainer this is likely. I fly a 6 seat twin and we can take off at 4750 but need to be under 4,513 to land.
66
u/ncc81701 11h ago edited 11h ago
You burn fuel as you fly so you are lighter on landing than takeoff. On wide body airliners, close to 50% of the takeoff weight is fuel weight and you need to designed your landing gear to withstand multi-g (3+gs) landings (takeoff need to only be designed around 1g). So if you need to design the landing weight to be the same as your takeoff weight, you will need a substantially larger and beefier landing gears. Unless you need to use that landing gear performance, the extra beefy landing gear is just dead weight that you have to carry around and burn more fuel for. The only time you can conceivably landing with full fuel is on an emergency right after takeoff and generally if you can get it into the air you have time to dump fuel to get it below landing weight limit. This is why your landing weight limit is lower than your takeoff weight limit.
33
u/nalc 10h ago
MLW is interesting for freighters because they prefer to keep it higher. They'd rather fly a max cargo load, partial fuel load from Tokyo to Anchorage, gas it up, then fly to San Francisco rather than fly a max fuel, partial cargo direct. Cargo won't pay a premium for nonstop and the economics of dollars per ton-mile are better.
9
u/SecureThruObscure 9h ago
Yep. Long haul is economically viable for time sensitive loads (and people), but an hour or two stopover to refuel the plane and pilots (and get rid of some waste…) is a marginal expense.
It costs a lot more to shave off those few hours. Cheaper to promise a 14 hour airport to airport window and have a few hours for… mass exchange? We’ll call it, for the pilots.
2
u/quocphu1905 5h ago
Not to mention those stopovers are also major sorting hubs where the aircraft will have to stop to unload cargo and load new ones anyway so it actually is way more beneficial to do a stop over.
3
u/jeffbell 10h ago
That's a good point about the g forces on landing.
Even the roughest take off is smoother than the average landing.
3
u/climb-a-waterfall 11h ago
I realize there is no one answer, but roughly what fraction of the total takeoff weight is made of fuel?
12
u/TheA350-900 10h ago edited 10h ago
On an A380, of the 560-ton MTOW, 250 tons is max fuel and passenger and cargo load is approximately 80–90 tons. For an aircraft specialized for ultra-long flights like the A350-1000ULR, it is a 320-ton MTOW with 130 tons of max fuel. So, in general, it is a bit less than half of the maximum weight.
2
u/Guadalajara3 8h ago
Depends on the type but commercial passenger aircraft doing domestic routes in the US maybe about 1/3 of the takeoff weight is fuel. The rest is airframe passengers and luggage/cargo, known collectively and ZFW or zero fuel weight.
Take off weight = fuel load + zfw
Take off weight is limited by the lesser of the performance limit or landing weight
16
u/Specialist_Reality96 10h ago
Yes, the limitation is structural, the engineers put a bit of a buffer in in case the monkeys up the front smack it down a bit harder that they should. There is also a hard landing inspection if the goobers up the front take their flying lesson from the penguins in Madagascar which is triggered if certain limits are hit on touchdown.
Even a lot of sail planes/ gliders have a lower landing weight than takeoff, they take water ballast to adjust the polar curve depending on conditions.
6
2
u/figurative_me 7h ago
Monkeys up front landing too hard?
Why you takin shots at Ryan Air like that?
9
u/ShaemusOdonnelly 11h ago edited 11h ago
Many comments mentioned landing gear loads already, but something less obvious is the go around. A go around is typically flown at high flap settings in airliners which creates drag and therefore reduces climb performance. In certain conditions (high temp, high altitude airfield) it is not uncommon that the landing weight (or rather, weight during the approach) is limited because you need to be able to comply with minimum climb gradients on a go around. This is one form of so called "performance limited MLW" whereas the gear stuff is "structural MLW".
19
u/Just-Smart-Enough 11h ago
Sure. Going up is less violent than coming down.
1
10
u/NotACompleteDick 10h ago
At takeoff the load shifts from the gear to the wings as the speed increases. At rotation the load fully transfers to the wings, where the majority of the fuel is held. The load decreases to zero. On landing the gear has to accelerate from 0 to about 150 mph at the same time that it also has to stop the descending weight of the aircraft. A very gentle landing can make this change gradual. But the hard landing limit on a 777 is 600 fps for an acceleration of 2.6g. Maximum landing weight is 575,000 pounds, depending on model, and higher for those not yet certified. So on an acceptable MLW landing the gear may have to handle nearly 1.5 million pounds force, or 750 short tons. Around twice the MTOW of 775,000 pounds. 777-8 will push MTOW to 805,000 pounds, the -9 is slightly less. If I though anyone was interested I could get the numbers for the A350, A330, B767, etc. But I think that explains the problem with landing weight well enough.
8
u/Top-Treacle9964 9h ago edited 9h ago
It not just common it's the norm. Aircraft have more fuel which is more weight at takeoff. The main limitation is the stress the structure takes when landing heavy. Gears can collapse structures can crack. after every overweight landing the aircraft has to go through a overweight landing inspection.
1
u/somehugefrigginguy 7h ago
Is this true of passenger flights? People are a relatively low density cargo. It doesn't seem like they'd be above landing weight at takeoff unless it's a long flight with a lot of fuel. But maybe I'm wrong.
3
u/Top-Treacle9964 7h ago
Yes it's this way for every airplane fuel is anywhere from 10 to 40 thousand pounds of fuel. It burns off leaving a few thousand pounds at landing. So fuel weight alone is the main reason why take off weight is higher then landing weight. It's all calculated I seen aircraft have to unload passengers and luggage because it would be overweight. Either at landing or at takeoff.
Bigger aircraft like 747 or 777 or any wide bodies have to dump fuel in emergencies or fly for hours doing circles to burn off fuel before landing.
1
u/FranseFrikandel 5h ago
Well, a short passenger flight might end up taking off below maximum landing weight, yes. But it still holds that the maximum takeoff weight is higher than maximum landing weight.
Sometimes there'll even be entirely empty flights that are extremely short just for moving to a different airfield for maintenance for example. Of course those take off already easily light enough to be below maximum landing weight.
Passenger planes are also already designed with the knowledge that passengers are low density, so it's not as if they end up designed in a fashion that it's hard or impossible to exceed maximum landing weight, especially when taking a lot of fuel.
1
u/Great_Specialist_267 3h ago
On the on the other side, some ferry flights are below minimum certified takeoff and landing weights (typical for an airliner stripped of its interior for conversion work).
6
5
u/Darth19Vader77 10h ago edited 9h ago
Very common.
The main limitation is going to be what the landing gear can handle. Landing gear are heavy and by the time airplanes land they're at their lightest because they burnt most of their fuel, so to save weight they're designed to handle weight below their maximum takeoff weight when touching down.
Another limitation is infrastructure, runways may look like a normal slab of concrete, but they're actually very deep and are only designed to handle so much weight.
9
u/FlyingSceptile 11h ago
The FAA actually says that if you can take off at a weight, you have to be able to land at that weight. However it’s not to the same limits as Max Landing Weight (need it to be a softer landing, not as worried about over heating the brakes, etc). Max Landing Weight is basically the heaviest you can pound it into the pavement
17
u/ShaemusOdonnelly 11h ago
Also important: Overweight landings require maintenance afterwards. Structural MLW is the highest weight you can land without these or other restrictions.
3
u/shrunkenhead041 11h ago
Yes, because the landing gear is under way less stress on takeoff than it potentially would be for landing from a bad flare or getting shoved on the ground when a gust of wind dies out. Even many small planes have higher takeoff than landing weights, though the difference may only be a couple hundred pounds or less.
5
2
u/JPAV8R B747-400 11h ago
Extremely common. The 747 had a ~90,000kg difference between max takeoff and landing weight.
It’s common to design a plane to takeoff heavy, burn fuel, and land lighter.
Landing lighter than your max takeoff weight allows for less robust landing gear (among other things) because they’re not designed for landing at that heavier weight.
2
u/ContributionEasy6513 8h ago
Very common on wide body missions in particular.
You can certainly dispatch an a320 & 737 with a higher takeoff weight than maximum landing weight, however its not that common on most short-medium flights.
You can still land overweight in an emergency, it just requires additional inspections and being gentle. Wide body aircraft will often dump fuel in an emergency, narrow body need to either burn it off or land overweight.
What is the main limitation on how heavy an aircraft can be at landing?
The book.
Why?
The landing gear and its structures have limits (quite high and conservative), but at some stage will fail in a very expensive and spectacular way. (Linked Picture for illustration purposes).
There is also limitations on how much energy the brakes can absorb on landing. Sure you can cook them, but they aren't cheap and a real headache to get towed off.
https://www.facebook.com/groups/803385438510648/posts/1300244355491418/
1
u/Lonely_Fondant 3m ago
I’m surprised no one else has mentioned brakes. If you’re heavier, you’re also faster, and faster with more weight is a LOT more energy. Yeah, brakes may be designed to handle a heavy landing once, and runways are long, but if the brakes overheat, they may cause a fire (airplanes leak stuff that is flammable), which may in turn cause tires to either deflate or explode, both of which are dangerous.
2
u/PlayerOfGamez 5h ago
As always, the answer is weight saving. Landing gear can be made smaller and lighter if max landing weight is reduced. Since it is expected to burn fuel during the flight, for some airplanes the max takeoff weight can be higher than the max landing weight.
1
1
u/BeenThereDoneThat65 ATP I G450 I G550 I GV 10h ago
Two years ago Gulfstream revised the AFM and now you CAN land at Max takeoff weight (that would be a helluva trick) as long as the landing is under 1.3G there is no need for a landing gear inspection
1
1
u/alettriste 8h ago
Dynamic loads. At takeoff you are unloading the structure. At landing you have to add the inertia loads. Check some botckednlanding and see the wings flexing. And think that all the structure is undergoing the same shock
1
1
1
u/LigerSixOne 5h ago
There will never ever be a situation where the landing weight needs to be more than max gross, and max gross is limited by max takeoff weight. Then you work backwards, how much weight do you want save by lowering how much impact the plane can handle on the landing. And by lowering that requirement you just increased max payload.
1
u/Accomplished-Toe-468 2h ago
Very normal if not almost certain. Less stress trundling along the runway rather than impacting on it.
1
0
u/Zvenigora 10h ago
Weight and balance. The center of mass is more critical during landing and full tanks can cause it to be aft of acceptable limits for landing. If a premature landing becomes necessary one must first dump fuel.
0
u/Guadalajara3 8h ago
Cant release a flight planned to land at the destination above max landing weight. If the flight diverts halfway and didnt burn through all the planned fuel, it will be above max landing weight and airplanes can land overweight with captains emergency authority
-6
u/blizzue ATP, 121 11h ago
Doesn’t take any amount of brakes to takeoff.
8
u/ShaemusOdonnelly 11h ago
That's just wrong. The brakes absolutely need to be able to stop the plane at MTOW so if they were limiting, MTOW would be lower too.
1
u/nalc 10h ago
The design point for brakes is usually a high speed rejected takeoff at max gross weight, although that's considered an emergency (meaning the brakes need to stop the plane, but they don't need to ever function again)
There are videos out there of them testing it on the 747 which are kinda nuts
1
1
u/FranseFrikandel 5h ago
Well, v1 is almost always quite a bit slower than landing speed. So the amount of energy the brakes would need to absorb for a rejected takeoff is still less than for a landing at the same weight.
3
3
u/TwizzyGobbler 11h ago
what happens when you need to stop just before V1 & you’re at mtow
1
u/poser765 11h ago
V1 is a product of weight… and some other things.
3
u/TwizzyGobbler 10h ago
that is the point yes
2
u/poser765 10h ago
Yeah sorry. I failed to notice yours wasn’t a top level comment and was actually a reply. My mistake
2
3
-2
u/Distinct_Rope 11h ago
Consistently smooth going up.
Coming down is.. well.. consistent.
I wouldn't want to weigh the same coming down than going up. Landing legs don't taste good when they go crunch through the floorboards.
-5
u/FreshTap6141 10h ago
Only wide body aircraft can dump fuel for landing weight reduction from what I read, the 747 had fuel dumps rear the wing ends
683
u/Chomp3y 11h ago
Fat man can jump, fat man's ankles can not withstand the landing