Sponsor Message:
Aviation Technical / Operations Forum
My Starred Topics | Profile | New Topic | Forum Index | Help | Search 
727 Approach And Keeping The Engines Spooled Up  
User currently offlinesmartt1982 From United Kingdom, joined Nov 2007, 225 posts, RR: 0
Posted (1 year 8 months 2 weeks 3 days 19 hours ago) and read 4547 times:

Was recently watching a clip of an approach on a 727, looked like everything was ok but the captain had to prompt the FO to keep the no 1 and 3 engines spooled up and that the FO could bring back thrust on the No2 to control the speed.

On the ground the captain stated this it was necessary to keep No1 and No 3 spooled up in case of a go around. Anyone heard of this before, is this a normal requirement on the 727 or any three engine jets?

I know that it is essential to have engines spooled up in case of a go around but what I am wondering is if it is common for the 727 to able to keep the required approach speed with engines idle or very close to idle normally on the approach?

[Edited 2013-02-09 07:48:38]

24 replies: All unread, jump to last
 
User currently offlineLimaFoxTango From Antigua and Barbuda, joined Jun 2004, 792 posts, RR: 2
Reply 1, posted (1 year 8 months 2 weeks 3 days 18 hours ago) and read 4520 times:

Unlike newer engines of today, older type engines take longer to spool up from idle. Keeping thrust just above idle shortens that time. There have been cases where the mains actually touch ground during a go-around although it was commenced as high as 100ft AGL (which could even lead to a tail strike). Another important reason for that "positive climb" call.


You are said to be a good pilot when your take-off's equal your landings.
User currently offlinercair1 From United States of America, joined Oct 2009, 1327 posts, RR: 52
Reply 2, posted (1 year 8 months 2 weeks 3 days 18 hours ago) and read 4517 times:
AIRLINERS.NET CREW
CUSTOMER SERVICE & SUPPORT

How old is the video?

About a year after intro, the 727 suffered a number of crashes short of the runway. There were a number of factors identified - primarily related to high sink rate and transition of pilots from prop to jet. It also had to do with the limited navigation aids at airports at that time. Part of the design criterion for the 727 was short field operations - so it had the ability, inherent in the design, for steep descent. Couple that with a lot of pilots transitioning from prop/turboprop to jet and you ended up with a situation where the aircraft could be at a high sink rate if at a low power setting. In addition - the response of the engines to throttle up was very slow - when compared to conventional prop driven a/c many of these pilots were transitioning from - which is nearly instantaneous. One more factor - the "jets" were fast and really needed pilots to fly "by the numbers" - much more so than slower prop driven planes. The 727 was so responsive and such a nice plane to fly that pilots often did not realize this and were more lax than they should have been.

Keeping the engines spooled up - where they responded quickly to throttle demands was one approach to help with this transition. The procedure noted was one approach used. In addition - some operators limited flap setting - not allowing full 40 degree flaps which added drag, but not much lift.

So - I think the procedure you noted is the result of a number of factors, one being the response to throttle up compared to props.

BTW - the source of most of this is a book I just finished - older - but interesting - called "Loud and Clear". There is another one specifically about the 727, but I've not been able to find a copy.



rcair1
User currently offlinetb727 From United States of America, joined Jun 2005, 1615 posts, RR: 9
Reply 3, posted (1 year 8 months 2 weeks 3 days 15 hours ago) and read 4444 times:

Quoting smartt1982 (Thread starter):
On the ground the captain stated this it was necessary to keep No1 and No 3 spooled up in case of a go around. Anyone heard of this before, is this a normal requirement on the 727 or any three engine jets?
Quoting rcair1 (Reply 2):
Keeping the engines spooled up - where they responded quickly to throttle demands was one approach to help with this transition. The procedure noted was one approach used. In addition - some operators limited flap setting - not allowing full 40 degree flaps which added drag, but not much lift.

So - I think the procedure you noted is the result of a number of factors, one being the response to throttle up compared to props.

Yes it does help keep them spooled up but you normally would never really have them at idle in the 727 anyways when landing until within 10 feet of the ground otherwise you're gonna get a stinger of a landing. I start slowly bringing all of them them back at about 10 or so feet, some people cut number 2 to idle and then milk 1&3 back the last 10 feet.

Using #2 to control speed is a technique that is taught to keep from jockeying 3 engine controls around while on approach. #2 is centerline thrust, when you are flying an ILS and you get close to your targeted speed, you can use #2 to adjust without messing with any asymmetric thrust from 1 or 3 because they are off centerline. It's not much of an effect if 1 or 3 get out of whack but it's nice to just use one thrust lever after setting the other 2 and not touching them. Having all 3 levers lined up doesn't necessarily mean they are all putting out the same N1/EPR, they can be off upwards of an inch or so, I can't remember if we even have a limit published in our book but they never match exactly, at NW they could be up to 1 inch off. In addition you might not need the thrust you're going to get from 3 engines, one is enough to "fine tune" it.

It's also nice to have them spooled up late in the approach because when you close them, touchdown, then activate reverse thrust, the engine doesn't have time to spool all the way down and you almost immediately have good reverse thrust with not much delay for spool-up. Again, just one of the many little techniques and quirks that pilots have come up with the last 50 years now the airplane has flown.



Too lazy to work, too scared to steal!
User currently offline113312 From United States of America, joined Apr 2005, 573 posts, RR: 1
Reply 4, posted (1 year 8 months 2 weeks 3 days 12 hours ago) and read 4366 times:

In the 727, you would never have a stabilized approach with engine thrust near idle. Normally, thrust adjustments to control airspeed would be made with all three engines together. However, in icing conditions with both engine and wing anti-ice systems ON, a minimum amount of engine RPM is necessary to produce sufficient hot bleed air for the ice protection to be effective. It could be that this was the case in this video. Engine 1 & 3 are producing the bleed air for the wing anti-ice. In this situation, the technique of only adjusting #2 could be used when the need arises to decelerate to adjust speed or extend additional flaps. Once the next target speed was achieved, the thrust could than be matched and sufficient to maintain the desired speed AND bleed air requirement.

User currently offlineflight152 From United States of America, joined Nov 2000, 3402 posts, RR: 6
Reply 5, posted (1 year 8 months 2 weeks 3 days 12 hours ago) and read 4349 times:

Quoting 113312 (Reply 4):
In the 727, you would never have a stabilized approach with engine thrust near idle.

Or any other transport category aircraft. When in a normal landing configuration, the drag created by the landing gear/flaps creates a need for a large amount of thrust in order to stay on the glideslope at Vref.


User currently offlineGoBoeing From United States of America, joined Jun 2000, 2706 posts, RR: 15
Reply 6, posted (1 year 8 months 2 weeks 3 days 11 hours ago) and read 4325 times:

Quoting smartt1982 (Thread starter):

Was recently watching a clip of an approach on a 727

Just out of curiosity, do you have a link to the video?


User currently offlinestratosphere From United States of America, joined Sep 2007, 1653 posts, RR: 5
Reply 7, posted (1 year 8 months 2 weeks 3 days 11 hours ago) and read 4315 times:

At FedEx the valsan mod 727 the # 1 and # 3 engines are a JT-8-217 they have an approach idle feature that keeps #1 and #3 spooled higher after the gear comes down then after touchdown there is a 5 sec delay built in in case of a go around then it reverts back to low idle setting.


NWA THE TRUE EVIL EMPIRE
User currently offlineSpeedbird128 From Pitcairn Islands, joined Oct 2003, 1648 posts, RR: 2
Reply 8, posted (1 year 8 months 2 weeks 2 days 21 hours ago) and read 4087 times:

Quoting rcair1 (Reply 2):
Part of the design criterion for the 727 was short field operations - so it had the ability, inherent in the design, for steep descent.

Just out of interest, why was short-field ability coupled with steep descent?



A306, A313, A319, A320, A321, A332, A343, A345, A346 A388, AC90, B06, B722, B732, B733, B735, B738, B744, B762, B772, B7
User currently offlinercair1 From United States of America, joined Oct 2009, 1327 posts, RR: 52
Reply 9, posted (1 year 8 months 2 weeks 2 days 20 hours ago) and read 4059 times:
AIRLINERS.NET CREW
CUSTOMER SERVICE & SUPPORT

Quoting Speedbird128 (Reply 8):
Just out of interest, why was short-field ability coupled with steep descent?

I don't think the requirement was for a steep descent - but that the ability to do a steep descent - or get into one, was an artifact of the short field capability. I'm sure a 727 driver out there could comment better than I. My source is just reading about the design and some of the problems. The 727 was intended to get in and out of fields that other jets of the time could not. You could achieve a 1000-1500 ground roll on a landing in a loaded 727. Take-off - no so much I think.

Keep in mind - 'short field' was relative to the 707 and it's ilk.



rcair1
User currently offlineSpeedbird128 From Pitcairn Islands, joined Oct 2003, 1648 posts, RR: 2
Reply 10, posted (1 year 8 months 2 weeks 2 days 19 hours ago) and read 4049 times:

Quoting rcair1 (Reply 9):
- no so much I think.

Quite. I once witnessed a 727-100 departing out of JNB... it *just* cleared the LLZ antenna departing off 03L. If it made a couple hundred feet of climb a minute I would have been surprised. The B722 for me as an ATC was the worst climber ever, rating right up there with the BA11.

However, when inbound, the 727 was an approach-control-friendly plane...



A306, A313, A319, A320, A321, A332, A343, A345, A346 A388, AC90, B06, B722, B732, B733, B735, B738, B744, B762, B772, B7
User currently offlinetb727 From United States of America, joined Jun 2005, 1615 posts, RR: 9
Reply 11, posted (1 year 8 months 2 weeks 2 days 9 hours ago) and read 3823 times:

Quoting rcair1 (Reply 9):
You could achieve a 1000-1500 ground roll on a landing in a loaded 727. Take-off - no so much I think.

They eat up runway on takeoff, that's for sure. As far as that short of a ground roll, maybe 1500 with nosewheel brakes but those disappeared for the most part long ago. It will stop pretty quick and I am very impressed with the anti-skid braking on wet and snowy runways, best brakes I have flown so far in my career.

As far as the "crow bar arrival" or a steep descent, if you can see it in the window, you can land on it. The toughest thing to get in your mind at first is to get it as slow as you can then you can drop it, trying to make the field from 5-6000' and 10 miles at 250 knots isn't gonna happen. I like to throw the gear to slow down if I have to, I hate it when guys want to use flaps to slow.



Too lazy to work, too scared to steal!
User currently offlineViscount724 From Switzerland, joined Oct 2006, 25653 posts, RR: 22
Reply 12, posted (1 year 8 months 2 weeks 2 days 8 hours ago) and read 3791 times:

Quoting tb727 (Reply 11):
It will stop pretty quick and I am very impressed with the anti-skid braking on wet and snowy runways, best brakes I have flown so far in my career.

727s regularly operated from 5,000 ft. gravel (and often snow-covered) runways in the Canadian north for some years.

Pacific Western 721 combi here in the mid-1970s at Resolute Bay (YRB) at about 74 deg. N. Temperature probably around -40 (same in F and C) when that photo was taken.

Current weather:
http://www.weatheroffice.gc.ca/city/pages/nu-27_metric_e.html

http://www.pwareunion.com/images/aircraft/B727-YRB.jpg


User currently offlineMax Q From United States of America, joined May 2001, 4660 posts, RR: 19
Reply 13, posted (1 year 8 months 2 weeks 2 days 2 hours ago) and read 3656 times:

Seven years on the B727 and I never had an issue with not having enough power on approach for bleed air /engine and or wing anti-ice.


Not an issue, using #2 to control speed with 1 and 3 at a stable setting was something I very rarely saw, I don't see a problem with it though.


There really isn't that much thrust asymmetry with the outboard engines.


You absolutely must be spooled up on approach by 1000agl, 500 at the very latest, having said that the spool up time
on those JT8D's was not slow at all, they come up pretty quick, a LOT quicker than the MD80 and many other bigger fans.



The best contribution to safety is a competent Pilot.
User currently offlinerwessel From United States of America, joined Jan 2007, 2368 posts, RR: 2
Reply 14, posted (1 year 8 months 2 weeks 2 days 1 hour ago) and read 3644 times:
Support Airliners.net - become a First Class Member!

Quoting Max Q (Reply 13):
You absolutely must be spooled up on approach by 1000agl, 500 at the very latest, having said that the spool up time
on those JT8D's was not slow at all, they come up pretty quick, a LOT quicker than the MD80 and many other bigger fans

I think the point is that compared to the pistons that many 727 pilots had been flying earlier, the spool up time was *very* slow.


User currently offlineAA737-823 From United States of America, joined Mar 2000, 5873 posts, RR: 11
Reply 15, posted (1 year 8 months 2 weeks 2 days 1 hour ago) and read 3642 times:

Quoting LimaFoxTango (Reply 1):
Unlike newer engines of today, older type engines take longer to spool up from idle.

That is utterly false.

The JT-8D maximum spool time from idle to target (varies by temperature, and can be found in several dozens of charts in the engine maintenance manual) is specified at 6 seconds. A healthy engine will do it in less than four.

On a CFM56? Good luck with that.

And engine with a larger diameter fan has greater rotational inertia than one with a smaller diameter fan.
Have you ever taxied a 737-NG? It's a wearisome experience, waiting on engines to spool up to get you across an active runway. For this reason, many pilots won't pull the engines back to idle, unless they anticipate sitting still for a while.


User currently offlineMax Q From United States of America, joined May 2001, 4660 posts, RR: 19
Reply 16, posted (1 year 8 months 2 weeks 2 days 1 hour ago) and read 3634 times:

Quoting AA737-823 (Reply 15):
:31 your local time (15 minutes 18 secs ago) and read 7 times:

Quoting LimaFoxTango (Reply 1):
Unlike newer engines of today, older type engines take longer to spool up from idle.

That is utterly false.

The JT-8D maximum spool time from idle to target (varies by temperature, and can be found in several dozens of charts in the engine maintenance manual) is specified at 6 seconds. A healthy engine will do it in less than four.

On a CFM56? Good luck with that.

And engine with a larger diameter fan has greater rotational inertia than one with a smaller diameter fan.
Have you ever taxied a 737-NG? It's a wearisome experience, waiting on engines to spool up to get you across an active runway. For this reason, many pilots won't pull the engines back to idle, unless they anticipate sitting still for a while.

Well said.



The best contribution to safety is a competent Pilot.
User currently offlineb767 From Norway, joined Feb 2008, 127 posts, RR: 0
Reply 17, posted (1 year 8 months 2 weeks 1 day 17 hours ago) and read 3526 times:

Seems to remember reading somwhere that Pratt and Whitney modified the JT8D to have a shorter spool up time as a resault of the early accidents.Is this correct?

User currently offlinercair1 From United States of America, joined Oct 2009, 1327 posts, RR: 52
Reply 18, posted (1 year 8 months 2 weeks 1 day 12 hours ago) and read 3432 times:
AIRLINERS.NET CREW
CUSTOMER SERVICE & SUPPORT

Quoting rwessel (Reply 14):
I think the point is that compared to the pistons that many 727 pilots had been flying earlier, the spool up time was *very* slow.

That is correct - the comparison to other jets is not the issue - it was compared to that big radial hanging out there.



rcair1
User currently offlinePihero From France, joined Jan 2005, 4597 posts, RR: 77
Reply 19, posted (1 year 8 months 2 weeks 1 day 11 hours ago) and read 3421 times:
Support Airliners.net - become a First Class Member!

Quoting rcair1 (Reply 18):
it was compared to that big radial hanging out there.

that's not the reason the 727 was difdferent from earlier prop types that used to fly and that the 727 replaced : The main difference pilots had to cope with was the immediate tift one got from the propwash over the wing : instant lift, lift that you could only get on a jet with increased speed.
Most of the times, those JT-8s were at 60 - 70% N2, so that spool-up to go-around RPM wasn't really an issue. (the main instrument is an EPR indicator that doesn't give one the rotation of the engine )

Quoting AA737-823 (Reply 15):
On a CFM56? Good luck with that.

Thanks. It's eight seconds from idle. Did it for tyhe past eighteen years.

[Edited 2013-02-11 14:50:52]


Contrail designer
User currently offlineMax Q From United States of America, joined May 2001, 4660 posts, RR: 19
Reply 20, posted (1 year 8 months 2 weeks 1 day 8 hours ago) and read 3351 times:

Quoting Pihero (Reply 19):

that's not the reason the 727 was difdferent from earlier prop types that used to fly and that the 727 replaced : The main difference pilots had to cope with was the immediate tift one got from the propwash over the wing : instant lift, lift that you could only get on a jet with increased speed.
Most of the times, those JT-8s were at 60 - 70% N2, so that spool-up to go-around RPM wasn't really an issue. (the main instrument is an EPR indicator that doesn't give one the rotation of the engine )

That's a very good point Pihero and well explained.


Another factor with the early high sink rate 727 accidents was the use of speed brakes with landing gear and flaps extended, this made for an extremely high sink rare and was later prohibited.


Pihero, did you fly the B727 ? best wishes.



The best contribution to safety is a competent Pilot.
User currently offlinePihero From France, joined Jan 2005, 4597 posts, RR: 77
Reply 21, posted (1 year 8 months 2 weeks 23 hours ago) and read 3260 times:
Support Airliners.net - become a First Class Member!

Quoting Max Q (Reply 20):
Pihero, did you fly the B727

Alas, no.
I had to make a choice between it and the DC-4. I chose the latter for I thought that was the last chance to fly a daddy's plane, thinking there would be other opportunities. I was wrong ... because when I had a command slot, the 320 was there and that time I made a choice for the newest technology.
A lot of my friends flew it and loved it but a pilot needed - needs - to be ten miles ahead of it : it had superb aerodynamics for its time but, as one of my classmates used to say : you fly in fact two airplanes : one with fighter performance when clean and one very draggy beast with flaps down in which you wouldn't want to be on the low side of the thrust/drag curve.



Contrail designer
User currently offlinercair1 From United States of America, joined Oct 2009, 1327 posts, RR: 52
Reply 22, posted (1 year 8 months 2 weeks 20 hours ago) and read 3190 times:
AIRLINERS.NET CREW
CUSTOMER SERVICE & SUPPORT

Quoting Pihero (Reply 19):
that's not the reason the 727 was difdferent from earlier prop types that used to fly and that the 72

Doh. I knew that. Just forgot it (seems to come with age...) Thanks Pihero!



rcair1
User currently offlinercair1 From United States of America, joined Oct 2009, 1327 posts, RR: 52
Reply 23, posted (1 year 8 months 2 weeks 20 hours ago) and read 3189 times:
AIRLINERS.NET CREW
CUSTOMER SERVICE & SUPPORT

Quoting Pihero (Reply 21):
you fly in fact two airplanes : one with fighter performance when clean and one very draggy beast with flaps down in which you wouldn't want to be on the low side of the thrust/drag curve.

Very nicely said.



rcair1
User currently offlineMax Q From United States of America, joined May 2001, 4660 posts, RR: 19
Reply 24, posted (1 year 8 months 2 weeks 11 hours ago) and read 3013 times:

Quoting Pihero (Reply 21):

Alas, no.
I had to make a choice between it and the DC-4. I chose the latter for I thought that was the last chance to fly a daddy's plane, thinking there would be other opportunities. I was wrong ... because when I had a command slot, the 320 was there and that time I made a choice for the newest technology.
A lot of my friends flew it and loved it but a pilot needed - needs - to be ten miles ahead of it : it had superb aerodynamics for its time but, as one of my classmates used to say : you fly in fact two airplanes : one with fighter performance when clean and one very draggy beast with flaps down in which you wouldn't want to be on the low side of the thrust/drag curve.

Yes, it was a great Aircraft, it could be unforgiving as you say and you had to stay ahead of it but it was the most enjoyable aircraft I have flown.



but I do envy you flying the DC4. That must have been a very rewarding experience from a very different generation



The best contribution to safety is a competent Pilot.
Top Of Page
Forum Index

Reply To This Topic 727 Approach And Keeping The Engines Spooled Up
Username:
No username? Sign up now!
Password: 


Forgot Password? Be reminded.
Remember me on this computer (uses cookies)
  • Tech/Ops related posts only!
  • Not Tech/Ops related? Use the other forums
  • No adverts of any kind. This includes web pages.
  • No hostile language or criticizing of others.
  • Do not post copyright protected material.
  • Use relevant and describing topics.
  • Check if your post already been discussed.
  • Check your spelling!
  • DETAILED RULES
Add Images Add SmiliesPosting Help

Please check your spelling (press "Check Spelling" above)


Similar topics:More similar topics...
Engines Under The Wing And On The Tail At Once posted Wed Nov 18 2009 17:35:36 by YYZALA
Keeping The Plane Straight On Takeoff And Landing? posted Thu Nov 10 2005 03:29:34 by SuseJ772
Flying On Half The Engines The Airplane Has posted Thu Feb 7 2013 20:41:33 by c5load
Airlines Not Painting The Engines Of 737-200's... posted Sun Nov 18 2012 15:02:10 by gilesdavies
Headwinds On Approach And Landing posted Sun Oct 28 2012 12:59:22 by LU9092
MRC And LRC, Winds For One And Not The Other! posted Thu Jul 12 2012 10:52:21 by smartt1982
Q.VARIG 747-341s And 747-441s Engines Design. posted Sat May 5 2012 13:08:15 by dennys
Which Way The Engines Spin posted Sun Feb 26 2012 19:40:39 by homsar
Love Field Approach And Departure Routes posted Fri Dec 16 2011 11:16:24 by william
Approach, And Departure, No Landing. posted Fri Sep 2 2011 17:41:27 by WarRI1

Sponsor Message:
Printer friendly format