FalconBird
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BAE-146 And Avro Without Leading Edge Slats

Sun Mar 30, 2008 1:36 am

Forgive me if this has been posted before, but why didn't BAE fit the 146 and the Avro with leading edge slats for possible extra lift on shorter runways?
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Starlionblue
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RE: BAE-146 And Avro Without Leading Edge Slats

Sun Mar 30, 2008 6:53 am

They have enough lift anyway?

My guess is that the extra weight and complexity negated the savings.
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Tristarsteve
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RE: BAE-146 And Avro Without Leading Edge Slats

Sun Mar 30, 2008 8:18 am

A lot of the smaller jets don't have slats.
Fokker 100, Gulfstreams, Smaller DC9s, BAC 111.
Slats are heavy and complicated, makes sense. It becomes a problem in the winter as these aircraft are much more sensitive to frost and ice on the wings and need care when deicing.
 
hotelmode
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RE: BAE-146 And Avro Without Leading Edge Slats

Sun Mar 30, 2008 10:16 am

The 146 wing is optimised for take off performance not high cruise speeds, so it simply doesnt need them.
 
troubleshooter
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RE: BAE-146 And Avro Without Leading Edge Slats

Mon Mar 31, 2008 3:41 pm



Quoting Hotelmode (Reply 3):
The 146 wing is optimised for take off performance not high cruise speeds, so it simply doesnt need them.

Correct. Originally, the BAe146 was designed as a military freighter with short take off and landing capabilities.
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Jetlagged
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RE: BAE-146 And Avro Without Leading Edge Slats

Mon Mar 31, 2008 8:40 pm



Quoting Troubleshooter (Reply 4):
Correct. Originally, the BAe146 was designed as a military freighter with short take off and landing capabilities.

The 146 was not designed as a military freighter. The freighter design came much later. It was originally intended as a feederliner (the term "regional jet" had not yet been coined). It was specified to be capable of operation from rough strips. It was also designed to be quiet. LE devices would be prone to damage on rough strips and reverse thrust could kick up a lot of debris. Both features increase noise.
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Airgypsy
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RE: BAE-146 And Avro Without Leading Edge Slats

Tue Apr 01, 2008 2:21 am

The constant radius leading edges made their appearance on LearJets and were very effective and efficient. I'm supprised more aircraft aren't sporting them.

The secret of lift on the BAe-146 is the aft translation of the flaps prior to lowering. Large wing area increase. Its part of that race car sound that passengers enjoy. Caused by the trailing edge seals on the ground spoilers vibrating against the top of the flaps as they go by. A large stainless steel reed instrument.

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Viscount724
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RE: BAE-146 And Avro Without Leading Edge Slats

Tue Apr 01, 2008 2:58 am



Quoting Troubleshooter (Reply 4):
Originally, the BAe146 was designed as a military freighter with short take off and landing capabilities.

Do you have a source for that? I can't ever recall reading that in any history of BAe146/Avro RJ development. Everything I've seen says that the original design was intended as a high-wing feeder-liner, with no mention of military or cargo applications.
 
BAE146QT
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RE: BAE-146 And Avro Without Leading Edge Slats

Tue Apr 01, 2008 5:48 pm



Quoting Airgypsy (Reply 6):
Its part of that race car sound that passengers enjoy. Caused by the trailing edge seals on the ground spoilers vibrating against the top of the flaps as they go by. A large stainless steel reed instrument.

Is that what that is? I never really found it noteworthy, but it sounds like a very raspy V6.

Quoting Viscount724 (Reply 7):
Everything I've seen says that the original design was intended as a high-wing feeder-liner, with no mention of military or cargo applications.

I agree. The original De Havilland design called for a short-range (and mostly domestic) airliner to cope with routes/journeys that cars or trains might normally be used for, back in the days when we used to burn kerosene for our amusement and everyone was supposed to fly about the place. HS (and later, BAe) obviously found a market for it despite OPEC sticking their hand up everyone's skirt.

The 146-STA was the military bird and was a production-line conversion.
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prebennorholm
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RE: BAE-146 And Avro Without Leading Edge Slats

Tue Apr 01, 2008 6:17 pm



Quoting FalconBird (Thread starter):
...why didn't BAE fit the 146 and the Avro with leading edge slats for possible extra lift on shorter runways?

BAe chose a wing profile with the shape of "half of a leading edge slat extended".

It has a lot of benefits: Lower weight, lower MX costs, much simpler icing management to name a few. And it is of course much cheaper to build.

They sacrifice on cruise speed. And on fuel efficiency on longer routes.

But for a plane, which is intended for short routes, the benefits can easily outdo the disadvantages. On short routes the weight advantage alone will easily neutralize the fuel efficiency disadvantage.

On a 500nm sector a BAe-146 is typically five minutes slower than an MD-80 or A319.

Often they gain (most of) those five minutes by not taxiing the last 2-3,000 feet to the runway end for take-off, but begin take-off roll somewhere on the middle of the runway. That saves a lot of fuel as well.

The BAe-146 wing airfoil section is a disaster at high Mach numbers. So they just keep it well below Mach 0.7.
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troubleshooter
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RE: BAE-146 And Avro Without Leading Edge Slats

Thu Apr 03, 2008 4:42 pm



Quoting Viscount724 (Reply 7):
Do you have a source for that?

I did my 146 maintenance course nearly eight years ago. Our english instructor was a former worker on the 146 with British Aerospace and he told us about the development.

Look at the landing gear and tell me if you find any other civil jet with a similar strong gear fitted.

But as I don´t know it for sure and have no "waterproof" source to quote, I will stand corrected if somebody knows it better.
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BAE146QT
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RE: BAE-146 And Avro Without Leading Edge Slats

Thu Apr 03, 2008 5:16 pm



Quoting Troubleshooter (Reply 10):
any other civil jet with a similar strong gear fitted.

It certainly wasn't designed with the military as it's primary customer, (unlike the 747!) but I'm with you there on that monster trailing link system, so I can see the logic. However, this was orignally for short and (possibly) rough field performance in the civil sector. But who knows? Maybe the designers did have military applications in mind - it would make sense from a commercial point of view.

But it's still true that the STA came well after the first -100 flew.

BTW, I'm currently scratch-building a 146-3 in 1:25 scale, which gives a fantastic opportunity to model that gear. It's only taken four attempts to get it right.  Yeah sure The only thing I have seen that comes close was designed to land on a carrier - the F/A-18.
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Jetlagged
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RE: BAE-146 And Avro Without Leading Edge Slats

Thu Apr 03, 2008 5:37 pm



Quoting BAe146QT (Reply 11):
BTW, I'm currently scratch-building a 146-3 in 1:25 scale, which gives a fantastic opportunity to model that gear.

That's quite a monster, over 4 ft long. What are you building it out of? At that scale you could use real hairdryers for the engines.  Wink
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tdscanuck
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RE: BAE-146 And Avro Without Leading Edge Slats

Fri Apr 04, 2008 1:13 am



Quoting BAe146QT (Reply 11):
It certainly wasn't designed with the military as it's primary customer, (unlike the 747!)

The 747 was never designed for the military. That was the C-5 and Boeing's equivalent entry (which was a different plane than the 747). The 747 looks like it does because, at the time, Boeing thought it would be shortlived as a passenger aircraft due to the development of the SST and Boeing assumed they'd be selling it mostly as freighters later in life. Turned out they were right, just off by about 30 years.

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