A question that keeps me awake at night. I see two different approaches to the landing gear in those two airliners. ATR went for "An-22 type" while Dash-8 decided to copy An-24. My question is why? Both planes were developed approximately at the same time, so it can't be a scientific development. Both are intended for the same markets. I don't see any advantages (or disadvantages) in aerodynamics. Why the two companies chose two different approaches? What are the pros and cons of those solutions?

And a bonus question I've been searching for on the Internet but couldn't find the answer to. Can any (or both) of those airliners land on unpaved runways? I wanted to say "like An-24" but that tank can land on anything, so maybe not a fair comparisson. And if they can, do they?

The ATR undercarriage is much lighter but has a narrower track. DHC traditionally preferred a wider track and longer stroke ( 16 inches ) for good crosswind capability and rough-field but at the cost of more complex engineering. The Dash suffered a rash of main-gear collapses in the mid-1980s which required a downlock modification.

Both types are certificated for unpaved operations, but the ATR's was obtained much later and is mainly concerned with gravel and compacted sand. The manufacturer themselves admit it wasn't originally designed for those conditions.

Whereas a Dash will operate from grass:

https://www.youtube.com/watch?v=FBFgeAIi1Kk

One doesn't collapse every other landing

I always thought had Bombardiar kept the gear from the Dash 300 they wouldn't have had all those gear issues on the Q400....can someone explain why they went with a different design?

ELBOB wrote:

The ATR undercarriage is much lighter but has a narrower track. DHC traditionally preferred a wider track and longer stroke ( 16 inches ) for good crosswind capability and rough-field but at the cost of more complex engineering. The Dash suffered a rash of main-gear collapses in the mid-1980s which required a downlock modification.

Both types are certificated for unpaved operations, but the ATR's was obtained much later and is mainly concerned with gravel and compacted sand. The manufacturer themselves admit it wasn't originally designed for those conditions.

Whereas a Dash will operate from grass:

https://www.youtube.com/watch?v=FBFgeAIi1Kk

Ooooooooooh! Wider track! Thank you! I didn't even think about that! And thanks for the video. I couldn't find any videos showing DHC landing on unpaved runways.

ATR have a trailing link landing gear, which leads to much nicer landings than the Dash, however both gears are closer together on the ATR which makes it a bit of a nightmare
to keep on the runway centre line in
crosswind situations.

The Dash landing gear has shock absorbers that might as well not be there, has anyone actually had a nice landing on a dash? ATR has pretty good shock absorbers, it's very well sprung.

Wider track as mentioned, but there is another thing.

The Dash-8 style gear has longer legs and needs to be beefier, adding weight to the gear itself. On the plus side, loads are transferred directly from the wing to the gear. With the ATR style gear, loads are transferred through the central fuselage, adding weight in that area.

BREECH wrote:

A question that keeps me awake at night. I see two different approaches to the landing gear in those two airliners. ATR went for "An-22 type" while Dash-8 decided to copy An-24. My question is why? Both planes were developed approximately at the same time, so it can't be a scientific development. Both are intended for the same markets. I don't see any advantages (or disadvantages) in aerodynamics. Why the two companies chose two different approaches? What are the pros and cons of those solutions?

The ATR gear is lighter for being shorter, but the pod for it does add to drag by increasing the frontal section. The DHC-8 effectively "hides" the retracted gear behind the engine, so less frontal area and hence reducing drag, at the cost of a longer and heavier leg. But, given the ATR's cruise speed and typical route profile, light works. The design trade-off for the ATR evidently said that this drag penalty was acceptable for the reduced weight, while the DHC team decided on less drag, wider track but higher weight.

In addition to what's already been said, the ATR gear design is also structurally less efficient.
Basically, on the Dash 8 design, you're putting the load of the aircraft weight into the wing spar, which is where the load is borne in flight anyway.
On the ATR, however, much, much more structure must be added to the belly of the fuselage, to support the weight transfer from wing spar to main gear upon touchdown. And all of that is structure that isn't necessary in the Dash design.
That doesn't make the ATR a "bad" design, of course. Just pros and cons.

Luftymatt wrote:

ATR have a trailing link landing gear, which leads to much nicer landings than the Dash, however both gears are closer together on the ATR which makes it a bit of a nightmare
to keep on the runway centre line in
crosswind situations.

The Dash landing gear has shock absorbers that might as well not be there, has anyone actually had a nice landing on a dash? ATR has pretty good shock absorbers, it's very well sprung.

I’ve had plenty of good landings with the Dash. The majority were just average though with a few in there that popped open overheads.

They told us in initial you’d never consistently land the airplane smoothly and it turned out to be true.


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DashTrash wrote:

Luftymatt wrote:

ATR have a trailing link landing gear, which leads to much nicer landings than the Dash, however both gears are closer together on the ATR which makes it a bit of a nightmare
to keep on the runway centre line in
crosswind situations.

The Dash landing gear has shock absorbers that might as well not be there, has anyone actually had a nice landing on a dash? ATR has pretty good shock absorbers, it's very well sprung.

I’ve had plenty of good landings with the Dash. The majority were just average though with a few in there that popped open overheads.

They told us in initial you’d never consistently land the airplane smoothly and it turned out to be true.


Sent from my iPhone using Tapatalk

Whilst what you were told is true, a good landing in a Dash does seem to be pretty few and far between.

TropicalSky wrote:

I always thought had Bombardiar kept the gear from the Dash 300 they wouldn't have had all those gear issues on the Q400....can someone explain why they went with a different design?

There were two styles of gear on the 300; the basic leg, upgauged from the 200, and the 311's legs which rake aft to give slightly more CoG range on the ground. But that was at its limit and the 400 needed a new beginning, and also changed to Menasco who had different design patterns than Dowty.

That swept back was what made it so sexy.....did Dowty not bid on the Q400 or Bambardier just went with in a different direction in terms of design partner?

ELBOB wrote:

TropicalSky wrote:

I always thought had Bombardiar kept the gear from the Dash 300 they wouldn't have had all those gear issues on the Q400....can someone explain why they went with a different design?

There were two styles of gear on the 300; the basic leg, upgauged from the 200, and the 311's legs which rake aft to give slightly more CoG range on the ground. But that was at its limit and the 400 needed a new beginning, and also changed to Menasco who had different design patterns than Dowty.

I think it was just financial; Menasco were being very aggressive on bids in the early 90s, they also displaced Dowty half-way through the Fokker 100's production.