I work just near an airport, so I see aircraft landing all the time. The approach speed of the 737 seems much higher than that of the 777 or any other jet airliner seen here, even the 717 which seems counter-intuitive. I'm curious why Boeing designed the aircraft this way. Surely a slower approach speed would reduce wear and tear on the aircraft? Does anyone have any idea?


The passenger jets which regularly land here are the 717, 737, 777 and A320. FWIW the 737 aircraft are all 738 I think.

Rob, could the relative size of the aircraft be creating a perception issue? Stating the obvious, the 777 is a LOT bigger than the 737 so would appear slower (I think).

From the figures I've seen online, the approach speed of the 737 is actually higher than the 717, 777 and A320. The difference seems to be around 10-15 knots, so whether it's possible to actually notice the difference between 140 knots and 155 knots, I'm not so sure. I agree that the 777 is a very big plane. By the same logic though, you'd expect the 717 to look a bit faster than the 737, but it doesn't. Maybe it's all in my head.

Age of the design for one thing. The speeds are somewhat dependent on the prior design of the original B737 design.

The original B373-100's (1956) operating empty weight (OEW) was ~28,000 kg with a wing span/area of 28m/91msq. Range 2800Km. Max Pax 124. Max TO (MTOGW) 50,000 kg.

The B737 MAX (2016) OEW is ~45,000 kg with span/area of 36m/127 sq M. Range 7000+ Km. Max Pax 220+. MTOG = 88,000 kg.

Very roughly, over the years that's a one-third increase in weight and potential payload with only about a one-fourth increase in total lift potential. The difference has gotta be made up by increasing all critical speeds.

It's not just Vapp (approach speed), but also required runway length and additional brake/reverser wear and maintenance costs associated with the extra speed.

[E=M x C squared -- A few extra knots equals energy-squared to be dissipated on landing and TO aborts.]

One of the current B737 MAX issues, and a factor throughout the 737's life, has been to maintain as much commonality as possible so as to use the original certificate -- which is a VERY expensive thing to replace.

You must appreciate that the original B737 design was for a short-range, small airport, light weight, hub feeder with minimal gear height to facilitate baggage handling without ground equipment. No main gear doors enhanced critical single-engine take-off performance but created a drag factor at high cruise speed.

With those as a part of the equation you may see that newer aircraft designs may have an advantage in lift efficiency and lower critical speeds. The newer aircraft have no or less dependence on an older original certificate/design.

There's many compromises in design and the economy of operation, maintenance costs and certification. What if the B737 MAX had been a clean-sheet design with all of the advantages of 50 years of advances in aviation. That's been the great advantage of the much newer Airbus A320 family.

Right, that makes sense. So presumably the same applies to other stretched aircraft designs where the lift hasn't increased.


Hopefully matter isn't being annihilated.


Although given what this debacle has cost, you have to wonder whether a new aircraft would have been cheaper - or a new certificate.


Yep, hence the odd nacelle design. The lack of main landing gear doors is a surprising design compromise which I only noticed when someone else mentioned it. I wonder how much fuel they could save if the gear was covered?


In the same way that Boeing could learn from the design faults of the Comet, I've no doubt that Airbus learned from the design issues of the 737. At the moment Boeing seems to have a need to learn from their own mistakes.

And a fascinating one too. Lots of moving parts and decisions to consider.

First, consider the mission. IIRC, the design goal was for a hub feeder that would make about five, 180 mile legs per day and need minimal service and ground support equipment at outlying terminals.

Second, extending and retracting landing gear consumes less than 60 seconds per flight but all that monkey motion consumes a disproportional amount of the maintenance time and is a critical system for dispatch. Eliminating most of the gear door mechanical and hydraulic systems 5-6 times per day is a significant advantage.

The third factor directly involves payload performance and MTOGW. Payload is constrained by five performance items; two are takeoff issues. The fixed given in takeoff performance is available runway length.


Takeoff weight on a given runway must allow for the loss of an engine at decision speed (V1) and then to either:
- stop on the remaining runway or
- climb away clearing all obstacles

The first thing that happens on liftoff is to open the large main landing gear doors which imposes a significant drag (payload) penalty. The benefit of having no gear doors 5-6 times a day outweighed the cruise speed penalty for the purpose of that mission. That worked great so long as the aircraft was operated as a hub-feeder; then the industry plan and the mission changed!

The B737 is over 60 years old. It still does what it was designed to do very well. A lot of changes have occurred in both technologies and the changing economic issues that had to be considered in continuing to support that design. Aircraft aren't built or airlines started to move people and cargo quickly from place to place; it's done to make money doing so.

Aviation's still the safest form of transportation.

Interesting that few other large passenger aircraft designs made the same compromise though.


True. I wonder how the landing gear drag of the 737-800 works out on routes like Sydney to Perth or Sydney to Queenstown in New Zealand? According to Wikipedia, the longest 737-800 flight in the world is from Panama to San Francisco. interestingly, the longest A320neo route is shorter, but the longest A321neo route is longer (Montreal to Nice).


Agreed!

Consider the 'hub-to-hub' companion aircraft of that era -- the B727. Short gear legs for easy ground servicing, integral boarding ladder where needed, cleaner/faster aerodynamics for longer routes and a third engine which alleviated SOME of the lose-of-engine payload issues (uses multi-engine rather than two-engine rules).

Add the B757 for long 'skinny' routes and the B747 for trans-oceanic service and the stable's full. The two-engine wide bodies (B767, A350, B777, etc) didn't arrive until new rules for ETOPS routes were approved for oceanic routes.

The various short and long versions were low-cost tweaks to optimize aircraft types (maintenance, parts and training costs) for individual carriers and/or market dominance.

Aside from the max and/or economic performance of an aircraft, the major issues with routes are whether the operator 'owns' the rights to a route -- often defined by 'owning' time slots and gates at the destinations. Some times an airline may have gates and slots it's not using for economic reasons and lease them to non-competing carriers. There's a lot of horse trading' goes on behind the curtain, especially when national flag carriers are involved.

Another interesting consideration for aircraft choices is geography. For example, USA, Russia and China have over-land routes servicing many intermediate population centers as well as both trans-continental and trans-oceanic service. Smaller nations may have only very short internal routes and very long international routes -- often over-water -- and have no economic need for the intermediate type aircraft. Add in the seat demands of the route. New Zealand? Canada? Australia? Japan? Europe? Different horses for different courses.

The way to make a small fortune in the airline business is to start with a very large one.

And the DC9 which evolved into the 717 and lost the rear door in the process, similar to that rear door on the 727.


And that's why there's airline "alliances" so the combination of airlines covers the world. As you imply, the national carriers always get priority.


Australia has all these issues, combined with a relatively small population. We have a huge country and a population which is mostly in a handful of capital cities. At the same time there's a need to service regional cities, but it's hard to do this economically. On top of that, all the international routes from the major capitals are long, so that Qantas is now pushing Airbus to see if the A350 will do the Sydney to London direct flight, and probably Sydney to New York direct. I just hope that they don't have regular economy on those routes.

To cover the variety of routes for Australia, Qantas has two versions of the Dash-8, the 717, 737, A330, 787, 747 and A380. The 747 is being retired, and sometime in the next couple of years they will start to replace the 737 with the A321. The A380 will be retired as well, so the whole fleet will be twin engine. I'm not sure what they will use in the A330 slot, perhaps a variant of the A321?

Personally I think that the Australian Government has to subsidise some of the flights to regional cities. If the decisions are left to economics alone, those airports will shut down. One curious phenomenon is Alliance, which runs F100 aircraft (mostly) between major cities and mines. It amazes me that it's more economical for mines to build a sealed airport which can land a Fokker F100 than to maintain accommodation for miners on site.

Richard Branson would probably disagree! He took a music fortune and turned it into an empire of airlines and trains. On the other hand I think the race to the bottom with airfares has had unfortunate side effects, with the quality of service and the comfort of seating dropping badly. I was astonished by the seats on the Lufthansa flight from Frankfurt to Barcelona; the thinnest aircraft seats I had ever seen. I'd have expected them on a military transport, but not a commercial airline. I never want to fly Lufthansa again, ever.

Yep, the real world's fascinating when you peek behind the curtains.

May you always either have tail winds aloft and large, soft seats or (preferably) own a Gulfstream G700.

https://www.youtube.com/watch?v=_O4jusKtW-8

I'm never likely to own a plane, but I should get a couple of flying lessons.

Experimental Aircraft Association

Check with these folks north of you. They may have some opportunities or ideas for you. The EAA has some free incentives for initial training. See if they have the Eagle Flight program there.

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Flying Start
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EAA 1308
Toowoomba, Queensland,
President: Michael Borgelt
Contact: 0746355784 | carol@borgeltinstruments.com
Meetings: Every 1st Saturday TBA
Location: Various
as advised
Toowoomba QLD 4350

Website: 1308.eaachapter.org
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I'm an E.F. Mentor pilot here. Many people want to sample the experience even if they don't have the time, resources or desire to carry through to a license. All are welcome.

Maybe you'll find someone that's beggin' for an excuse to make a cross-country flight to Canberra for lunch?.

Thanks for the suggestion! Toowoomba is a bit far from Canberra (I used to live in Brisbane, and it would have been workable from there). I should mention that I've had my hand on the controls a couple of times - once on a Drifter ultralight near Boonah in Queensland, and the L39 Albatros jet in the Hunter Valley. I don't think two aircraft could be much further apart! There's some flying schools in the Canberra region - I regularly see light aircraft doing circuits and bumps on Canberra Airport. There's also a 737 simulator which I'd like to try. I went up in a number of ultralights for photography purposes when my brother was editing the magazine for the (then) Australian Ultralight Federation.