Why are regional jets slow?
Thread Starter
Joined: Aug 2000
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From: Boston, MA, USA
Why are regional jets slow?
It has been mentioned often in the press etc, that one of the effects of the proliferation of regional jets has been the crowding/slowing down of air traffic because although they cruise at the same flight levels, the travel slower than full size jets.
Why do they fly slower? Apart from FD 328, which was derived from a turboprop plane, the other ones were directly built as jets, so why were they made to cruise at slow speeds?
Why do they fly slower? Apart from FD 328, which was derived from a turboprop plane, the other ones were directly built as jets, so why were they made to cruise at slow speeds?
Joined: Sep 1999
Posts: 5,552
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From: ME
When you build an aircraft you are faced with a number of choices, in this case the primary challenge is to build the most efficient aircraft that can operate from "shorter runways", or those that we can expect in regional areas.
This results in a trade off in the wing design, getting out of these airports is our prime concern, the time lost in the cruise on relatively short sectors isnt........
So you end up with a relatively slow cruise speed....
Mutt.
This results in a trade off in the wing design, getting out of these airports is our prime concern, the time lost in the cruise on relatively short sectors isnt........
So you end up with a relatively slow cruise speed....
Mutt.
)
Joined: Nov 2001
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From: Inside the M25
I thought Emb 145's were pretty nippy as well. Is it just that on regional routes, they don't go high enough for the good Mmo to show up?
I know 146's are slow, but there the aim really was short field performance .....
Can the assertion that regional jets are slow be backed up with some facts, please, for those of us who don't know them?
I know 146's are slow, but there the aim really was short field performance .....
Can the assertion that regional jets are slow be backed up with some facts, please, for those of us who don't know them?
Joined: Jun 2001
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From: Surrounded by aluminum, and the great outdoors
lookin at a few numbers...most will go high speed cruise or whatever at or above .80,....but normal cruise is below that .75 or .80 ain't making no difference on a 1 or 2 hour sector, and to go as "fast" as a regular jet (.80) or better...would burn more fuel and run higher egt's etc...etc...not worth the effort, or wear and tear on equipment
Joined: Nov 2001
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From: Inside the M25
I know. But the point I'm making is that the charge was levelled that RJ's are slow ... when 737 "classics" are slower. I think what I'm getting at is that a false assertion was implied in the question - "why are RJ's slow?" The answer is, they are the speed they are designed to be - which in some cases is faster than some non-RJ's.
Joined: Feb 2000
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From: Montreal
The CRJ's normally cruise between .74 and .77. The 200 series can make .80 much of the time if you want to burn lots of gas. They do require a fair bit of runway if there's contamination due to no leading edge devices.
The 700 series will go straight to FL410 and can make .80 cruise at most altitudes--but most people don't do that because the time saving on a 1hr leg will not be offset by the extra fuel burn. It also uses much less runway because it has slats.
As for the "reputation" of going slow, this likely comes from that "RJ" that is powered by four APU's.
From what I hear, they barely keep up with some of the new turboprops.
The 700 series will go straight to FL410 and can make .80 cruise at most altitudes--but most people don't do that because the time saving on a 1hr leg will not be offset by the extra fuel burn. It also uses much less runway because it has slats.
As for the "reputation" of going slow, this likely comes from that "RJ" that is powered by four APU's.
From what I hear, they barely keep up with some of the new turboprops.
Joined: Jun 2002
Posts: 6
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From: Staffordshire UK
Slow Regional Jets?
Could it be that manufacturers build slower regional jets firstly to utilise short runways, and secondly to keep within the stringent noise limits, especially in small regional airports close to populated areas.
With noise regulations becoming tighter it could be that manufacturers are keeping down noise and speed so that the market for aircraft in the smaller airports remains as high as possible.
Thirdly, i may just be very cynical!
happy flying
With noise regulations becoming tighter it could be that manufacturers are keeping down noise and speed so that the market for aircraft in the smaller airports remains as high as possible.
Thirdly, i may just be very cynical!
happy flying
Joined: Feb 2001
Posts: 1,064
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From: Hants, UK
From an ATC viewpoint, I often find I have to treat regionals differently to the 'bigger' jets.
Putting aside 146s, which are not great performers in any area, the CRJ/ERJ families are indeed no slouches when in the cruise, but they seem to be able to go up OR forward, not both. Climbing mach numbers seem to be in the range from M0.5 to 0.6, and then an acceleration to M0.75-0.77 in the cruise. Compare this to an MD80-90 or 737 which will climb AND cruise at M0.74+. This big difference in climb vs. cruise for RJs can make for some interesting catch-up scenarios for the unwary
Putting aside 146s, which are not great performers in any area, the CRJ/ERJ families are indeed no slouches when in the cruise, but they seem to be able to go up OR forward, not both. Climbing mach numbers seem to be in the range from M0.5 to 0.6, and then an acceleration to M0.75-0.77 in the cruise. Compare this to an MD80-90 or 737 which will climb AND cruise at M0.74+. This big difference in climb vs. cruise for RJs can make for some interesting catch-up scenarios for the unwary
