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Bigger Planes Use Shorter Rwy Than Smaller Ones?  
User currently offlinekurbitur From Iceland, joined May 2010, 66 posts, RR: 0
Posted (3 years 6 months 3 weeks 2 days 14 hours ago) and read 5110 times:

I was spotting today at Copenhagen Kastrup (CPH) and was close-up to the departing aircrafts at rwy 4 R.

I noticed SAS A321 and taxing to the 3rd exit to the beginning of the runway and 737-800

Than Continental 757 went for the second last taxiway into the runway with full throttle

Than some SAS Canadair CL-600 Regional Jets and Wideroe´s (De Havilland) went for the whole runway, with
nose gear almost licking the grass.

any guesses?




(took this one today of CO to EWR)

13 replies: All unread, jump to last
 
User currently offlineGiancavia From Vatican City, joined Feb 2010, 1310 posts, RR: 0
Reply 1, posted (3 years 6 months 3 weeks 2 days 14 hours ago) and read 5103 times:

Weight... some are fully loaded some arent.. some are better performing aircraft in certain weathers/elevations then others .. etc etc

User currently offlineChrisNH From United States of America, joined Jun 1999, 4083 posts, RR: 2
Reply 2, posted (3 years 6 months 3 weeks 2 days 14 hours ago) and read 5092 times:

Just a guess on my part, but the bigger wing surface on a 'bigger plane' would also help lift it into the air sooner than a small wing surface.

User currently offlineKcrwflyer From United States of America, joined May 2004, 3795 posts, RR: 7
Reply 3, posted (3 years 6 months 3 weeks 2 days 14 hours ago) and read 5022 times:

That runway's almost 11,000ft. I'd imagine all of the entrances used gave the pilots at least 8,000? They're all probably just doing what's most convenient for them. ORD uses intersection departures on a daily basis.

User currently offlineGiancavia From Vatican City, joined Feb 2010, 1310 posts, RR: 0
Reply 4, posted (3 years 6 months 3 weeks 2 days 14 hours ago) and read 4983 times:

When Im at luton regularly you have the tiny citations or hawkers backtracking and using the whole runway and then a ryanair 738 or an ezy A319 will just taxi straight onto the runway and do a short take off.

User currently offlinerfields5421 From United States of America, joined Jul 2007, 7571 posts, RR: 32
Reply 5, posted (3 years 6 months 3 weeks 2 days 13 hours ago) and read 4932 times:

It's a matter of power to weight ratio.

But it may also be a matter of airline operating policy. Some airlines require takeoff from the end of the runway and do not allow intersection takeoffs.

Bigger light planes with more power can takeoff faster with less runway than smaller heavy planes with less power which take more runway.

The CRJ-200 is well known for needing a lot of runway if full of pax, bags and fuel.

Bombardier's specs say the CRJ at MTOW needs

CRJ-200 ER - 5,800 ft
CRJ-200 LR - 6,290 ft

CRJ-700 701 - 5,130 ft
CRJ-700 701 ER - 5,500 ft
CRJ-700 701 LR - 6,072 ft

CRJ-700 705 - 5,833 ft
CRJ-700 705 ER - 6,105 ft
CRJ-700 705 LR - 6,378 ft

CRJ-900 - 5,833 ft
CRJ-900 ER - 6,105 ft
CRJ-900 LR - 6,379 ft

http://www.crj.bombardier.com/CRJ/en...sp?langId=en&crjId=200#performance


User currently offlineBLUEWHALE18210 From United States of America, joined Aug 2006, 237 posts, RR: 0
Reply 6, posted (3 years 6 months 3 weeks 2 days 13 hours ago) and read 4889 times:

1. Full takeoff Vs. Flex takeoff. The Flex uses more runway at a lower N1 setting which conserves engine parts.
2. The bigger plane might be loaded at a lower percentage and therefore has more excess thrust for a early rotation.
3. This escapes lots of people...but depending on the design of the airplane, smaller planes might need more runway.
For example a 737 is an Approach Catagory C aircraft, the Vref being between 120-140kt. CRJ-200, despite being smaller and less than half the weight, is Catagory D, Vref 140-160kt for lack of leading edge devices. That also meant a CRJ2 needs more speed on takeoff as well. CRJ9 is back to being CAT C.



JPS on A300-600RF A319/320 B737-400/800 B757-200F B767-300F CRJ-200/900. Looking to add more.
User currently offlineBMI727 From United States of America, joined Feb 2009, 15715 posts, RR: 26
Reply 7, posted (3 years 6 months 3 weeks 2 days 13 hours ago) and read 4889 times:

Quoting rfields5421 (Reply 5):
The CRJ-200 is well known for needing a lot of runway if full of pax, bags and fuel.

The lack of slats has a lot to do with that.

Quoting kurbitur (Thread starter):
any guesses?

It is a bit difficult to make any judgments just by watching, since probably almost all of those planes were using a derated takeoff to some degree.



Why do Aerospace Engineering students have to turn things in on time?
User currently offlineRussianJet From Belgium, joined Jul 2007, 7688 posts, RR: 21
Reply 8, posted (3 years 6 months 3 weeks 2 days 13 hours ago) and read 4866 times:
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Quoting Kcrwflyer (Reply 3):
That runway's almost 11,000ft. I'd imagine all of the entrances used gave the pilots at least 8,000? They're all probably just doing what's most convenient for them. ORD uses intersection departures on a daily basis.

  

Although there are a ton of potential variables, the most likely common denominator here was whatever was easiest from a traffic and taxy distance perspective.



✈ Every strike of the hammer is a blow against the enemy. ✈
User currently offlinedimik747 From United States of America, joined Nov 2010, 51 posts, RR: 0
Reply 9, posted (3 years 6 months 3 weeks 2 days 1 hour ago) and read 2764 times:

Flex/Derated takeoffs aside there is nothing really connecting small planes to shorter take off rolls unless they are designed that way. For example you could add a ge-90 on a 737 or on a crj-200 and it would take off very quickly, but if STOL isnt the particular mission of the airplane there is not much point adding a bigger wing and more high lift devices (and therefore more weight) just so it can take off on a short roll. The crj-200 for example is a much smaller airplane, but it has no leading edge devices so it requires much higher speeds and it seems to be doing just fine

User currently offlineB777LRF From Luxembourg, joined Nov 2008, 1300 posts, RR: 3
Reply 10, posted (3 years 6 months 3 weeks 1 day 12 hours ago) and read 2506 times:

Quoting rfields5421 (Reply 5):
It's a matter of power to weight ratio.


That is certainly part of the equation, but as the BAe-146 will testify it's only half the answer. The other variable is of course lift.

To elaborate, it's the design of a wing that determines the speed at which enough lift is generated to get an aircraft off the ground; bigger engines will only help reach that speed faster. Hence an aircraft with a poor thrust-to-weight ratio and a high lift wing might very well get off the ground quicker than a much more powerful, but low lift, ditto; Super-Cub vs F-15 is an excellent example.



From receips and radials over straight pipes to big fans - been there, done that, got the hearing defects to prove
User currently offlineairportugal310 From Palau, joined Apr 2004, 3575 posts, RR: 2
Reply 11, posted (3 years 6 months 3 weeks 11 hours ago) and read 2273 times:

I think some pilots just like the thought of having extra runway to play with...gives them more options or more runway to play with in some kind of emergency (whatever that may be).

Im sure human factors are involved in it, somehow

I would probably fall into that category, all ops specs aside



I sell airplanes and airplane accessories
User currently offlineGoBoeing From United States of America, joined Jun 2000, 2682 posts, RR: 14
Reply 12, posted (3 years 6 months 3 weeks 9 hours ago) and read 2243 times:

Quoting airportugal310 (Reply 11):
I think some pilots just like the thought of having extra runway to play with...gives them more options or more runway to play with in some kind of emergency (whatever that may be).

Im sure human factors are involved in it, somehow

I would probably fall into that category, all ops specs aside

Ohhh yeah.

One runway we sometimes use at an outstation absolutely has got to have something totally wrong in the performance data, because if we do a flaps 2 takeoff, the usual configuration in our airplane, we'll often pass over the departure end climbing through about 30 feet. With an engine failure at V1, we're supposed to be guaranteed 35' AGL by then. Absolutely no chance a rejected takeoff shortly before V1 would end in anything other than a runway overrun.

So, we do a longer taxi to the longer runway.


User currently offlineGoldenshield From United States of America, joined Jan 2001, 5970 posts, RR: 14
Reply 13, posted (3 years 6 months 3 weeks 2 hours ago) and read 2174 times:

Quoting BLUEWHALE18210 (Reply 6):
For example a 737 is an Approach Catagory C aircraft, the Vref being between 120-140kt. CRJ-200, despite being smaller and less than half the weight, is Catagory D, Vref 140-160kt for lack of leading edge devices. That also meant a CRJ2 needs more speed on takeoff as well. CRJ9 is back to being CAT C.

The CR7 is Cat C, but the CR9 is back up to Cat D. I'm assuming that Bombardier did some improvements on the -1000 so that it's brought back down to C again.

However, the above has nothing to do with taking off, hence why they are called Approach Categories.



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