737 descent without speedbrake?

[EIDAN]

Okay, I'l bite. What's wrong with using speed brakes? Stay high longer to save fuel and then rocket on down at the last minute. What's the big deal? Is this some kind of ol' timer traditional thing? If I'm not sopposed to use them why did they give 'em to me in the first place?

Why stay up at altitude longer with cruise thrust when you can be in a idle denscent? Sure specific fuel consumption will rise as you descend, but its still more fuel economic if you can fly with the throttles closed all the way from TOD in to 3-4 miles final. The only reason to stay up longer and descend at a higher speed (steeper descent gradient) would be if you have a high operating cost as compared to the fuel price.
But of course the speed brakes are there for a reason, use them if you have to. I try to use them as little as possible because evertime i use them i "waiste" energy, which normally means you have to spool up the engines earlier on the approach and burn more fuel. But if ATC keeps you high, or if you get a more direct route while in the descent, you will have to use them. But then again the only real speed brake on the 73 is the gear.
Just basic energy management.

 

[80/20]

Well put EIDAN, I agree 100% about how to plan the profile and use of speedbrakes/gear.

 

[FurloughedAgain]

Speedbrake usage in RJs.

Caveman,

Yours is very common reasoning among Comair captains. For what its worth I've never worked for an airline where speedbrakes (flightspoilers, whatever) are overused as much as they are here. With proper descent planning and energy management you very rarely have to use them.

They make a lot of noise, they make for a rough ride, they scare the customers.

As an old Cap'n on the DC9 told me (after smacking my hand), "That handle's only for when somebody screwed up son. If nobody screwed up, don't touch it!"

Law of primacy. I was taught to fly a jet without em'. As such it hurts like hell when I see folks use them so much.

Now, if only someone would teach RJ pilots how to land the airplane without rolling it on flatter than my prom date...

 

[767200]

Okay, I'l bite. What's wrong with using speed brakes? Stay high longer to save fuel and then rocket on down at the last minute. What's the big deal? Is this some kind of ol' timer traditional thing? If I'm not sopposed to use them why did they give 'em to me in the first place?

The FMS calculates the most fuel efficient climb/cruise/descent profile based on the index number. Staying high will NOT save fuel all the time. Moreover some people think that "flying higher" will also save fuel. Not necesarilly. Always fly your "optimum altitude". For instance, on a 727, flying 2000ft higher than your optimum will make you burn 2% more fuel, which is just as bad as if you were flying 200ft lower than your optimum.

 

[FurloughedAgain]

CRJ Whining

The "high tech" CRJ that Caveman and I are subjected to was not purchased with a VNAV (or even VPLAN) option. There is no input for cost index.

The company chooses cruise speeds based on the time of year (I believe .77 in the winter and .74 in the summer). The dispatchers do not look at individual flights to select efficient cruise speeds -- I sometimes wonder whether they even look at altitudes.

The airplane will calculate the rate of descent required to cross XYZ but that is based preliminarily on the preprogrammed data (.74/320KIAS and takes into account descent winds if the crew enters that data) and then, during the descent, on the existing rate of descent.

It will NOT calculate a constant rate of descent that can be used on arrivals with numerous crossing altitudes (such as the Korey3 into LGA), nor will it take into account barometric pressure or changing winds in the descent to give you a valid TOD point.

On the up-side, the RJ's FMS performs its calculations much much faster than the ancient FMS that the ol' 737-300s had.

Still, would've been nice to have the extra capability. I'll add it to my wish-list along with:

• leading-edge devices
• a F/O-side FMS head
• VNAV
• autothrottles
• an autopilot that can handle configuration changes or an ILS without suffering wild pitch excursions
• a decent cup-holder
• and a flight-bag compartment that sits on the floor rather than at shoulder-height.

(geez I sure whine a lot...)

and, by the way... who ever heard of a HOBBS meter in an airliner and who the HECK decided that F/Os should add oil to the engines at night??? If I wanted to work for Jiffy-Lube... and do I even need to MENTION the stupid yellow crew-bag condoms in order to stow our bags in cargo -- basically big yellow signs that say "Hey rampers! Search me for loose change!"

(ok i'm done whining now...)

 

[Caveman]

Thanks for the input. I agree with what's been said. I oversimplified when I said 'stay high and rocket on down'. What I was really asking is where did the idea come from that using speed brakes is bad form? Using them to overcome bad descent planning is a tad unprofessional but I was getting the impression that using them at all was against some old school tradition. Perhaps I misunderstood. I use them regularly as a part of descent planning in the terminal area particularly when assigned a slower speed, say 180 KIAS. A little speed brake on the descent is better than standing it on it's nose with flaps to keep it slow. Plus, when you level off and retract the spoilers you don't need as much thrust as if you had flaps hanging out. Technique I guess. Again, thanks for the input.

 

[Guppiedriver]

I use them regularly as a part of descent planning in the terminal area particularly when assigned a slower speed, say 180 KIAS. A little speed brake on the descent is better than standing it on it's nose with flaps to keep it slow. Plus, when you level off and retract the spoilers you don't need as much thrust as if you had flaps hanging out. Technique I guess. Again, thanks for the input.

Caveman,

Using the speedbakes as you suggest is not technique. Technique would be using the speedbrake to help the aircraft decelerate quicker or to increase the rate of descent without reducing the airspeed. You are suggesting that you can use the speedbakes instead of selecting the next appropriate flap setting for the speed assigned. Your company has published specifc speeds that you fly your 737 at, based on the numbers provided by Boeing. Speekbrakes out or not, slowing the aircraft below the recommended airspeed for a particular flap setting is wrong.

 

[FurloughedAgain]

Go Arounds Pay More Than Landings

Caveman,

You dont HAVE to select flaps at 214.9 knots. What's the big hurry to slow to 180 when they ask? Why not just reduce power and let the airplane slow?

If they ask you to slow and descend simultaneously, why not just reduce thrust to slow, and then (once slowed) begin the descent?

Obviously I dont care much for speedbrake usage -- but I also dont care much for folks who drop the flaps right at the maximum possible airspeed.

In the end I think you hit the nail on the head when you said the magic word: "technique".

There are 1000 ways to fly an airplane safely. You prefer speedbrakes in the terminal area. I prefer not to use them unless there is a necessity (i/e descending with anti-ice on).

I don't believe either is wrong. It's just a difference in technique.

... and by the way... I flew with a lot of old-school captains over the last 6 or 7 years -- Guys who flew for Eastern, Braniff, PSA, Piedmont, and Allegheny. There does, in fact, appear to be an "oldschool" belief that the use of speedbrakes is bad form. I got the hand-slap scars to prove it.

 

[Caveman]

Guppiedriver,

Let me give you an example. Min clean in the CRJ is typically about 180 KIAS. Flaps 8 or 20 is 215 max. Let's say I'm at an assigned 210 KIAS and 9000 ft (which is fairly normal for the terminal area). "CMR 123, descend and maintain 4000". The CRJ will not descend at a decent rate (say at least 1500 fpm) and stay at 210 KIAS. My choices are: pick a slower descent rate, flaps, flight spoilers or some combination of the three. I choose spoilers. Why? Because I'm 30 knots faster than min clean and I don't need the flaps for safe maneauvering. When I level at 4000 I'll need less thrust to maintain speed and altitude clean than I would with flaps 8 or 20. If I descend with flaps at 210 KIAS there is a decided nose down pitch attitude that is uncomfortable for the pax. That IS a technique and it's not wrong as you suggest.

Look, I'm not trying to argue about this I was just curious as to where this idea came from that using spoilers is bad form. CRM. Use all available resources. Under the right set of circumstances even flight spoilers can be effectively used as part of a planned profile. Sometimes I even use them when I screw up and almost miss a crossing restriction!

 

[Guppiedriver]

I would like to know how often 737-600/700/800 pilots are able to fly a complete leg without ever needing to use the speedbrake to descend, I did not think it was used very much, but some others say it is used all of the time.

Thanks.

Caveman,

Above is the original question.

Therefore, I had to assume that your answer was related to the 737.

It may be a dandy technique on the RJ, but nobody asked.


Gup

 

[Caveman]

Guppie,


I understand. Cheers......

 

[Snoopy58]

The CRJ will not descend at a decent rate (say at least 1500 fpm) and stay at 210 KIAS. My choices are: pick a slower descent rate, flaps, flight spoilers or some combination of the three. I choose spoilers. Why? Because I'm 30 knots faster than min clean and I don't need the flaps for safe maneauvering. When I level at 4000 I'll need less thrust to maintain speed and altitude clean than I would with flaps 8 or 20.

I agree that flaps would be a bad option for you, but why do you need to descend quicker than 1500 fmp??? If you get to your level-off altitude & have to push up power, you got there at least somewhat early; if it looks like you'll be droning at 4000' for a while, why hurry down with the S/B so you get there sooner only to then push up the power (sooner) & burn more gas? The 737 will only do about 1200 fpm at 210, or about 1600 at 250, and it's rare that we need to use speedbrakes in most terminal areas. Sometimes it happens, or sometimes it's useful (abeam the field at 10,000, cleared the visual #1), and cases like that toss out all the drag you got and play the speed & distance so you push up power for a stabilized approach but not miles sooner.

It's uncommon that ATC plans you (generic you, not you Caveman) into a corner that you have to use boards. If they're holding you high past your top-of-descent point, deal with it... go fast (the fuel's burned, but at least you get the speed) if you can, and if they want to make you high AND go slow all the way down, tell them that you may not be able to make the crossing restriction. They'll either waive the restriction, or the speed, or tell you to "do your best."

Or maybe you'll be #20 behind the guy who needs a 15 mile final fully configured... but not likely. ATC generally knows when they've goofed.

 

[MLBWINGBORN]

Why not just adjust rate of descent to maintain assigned or planned speed at flight idle?Plan your TOD based on that rate and ground speed..

Anything over 500 fpm is gravy according to ATC..Why give them more unless YOU need it?

Mike

 

[F/O]

Why would anybody use VNAV on the CIVET?? Save yourself a lot of grief and use V/S...and keep it niiiiice and smooth......

 

[Thedude]

Man I wish the controllers in the JFK area thought that anything over 500'fpm was gravy.

 

[English]

The use of speedbrakes is a crutch to cover for bad planning, either on ATC's or the pilot's part. It's bad form, IMHO. I learned when flying corporate that passengers hate it and are very uncomfortable with it. Now that I know that, I NEVER use them unless absolutely necessary. I think I've used them twice and hated every second of it. The 737 descends just fine under normal circumstances without them.

Now when I fly in the back on other airlines, I wince whenever the speedbrakes come out. Some guys actually add power with the speedbrakes out...I don't get it. I guess power management and efficiency are lost on some.

 

[80/20]

Most pilots want to glide down from cruise at idle without premature drag (speedbrakes). At the same time as they avoid getting down too early and burn extra fuel while dragging along at low altitudes. Some call the speedbrake handle “the lever of shame” or “pilot error correction handle”.

Many 737 pilots calculate top of descent with the 3X formula: Decent distance required is about 3 miles per 1000 ft. with 280 KIAS and no wind. Correct for wind by using +/-2 miles per 10 kts of tail/headwind. A completely programmed FMC with published arrival altitude restrictions, ISA deviations and winds at various altitudes will refine this even further through VNAV. VNAV also calculate the most economical profile by customizing climb, cruise and decent speeds through a number of sophisticated calculations. VNAV works fine as long as you don’t trust it 100%. Back VNAV up with the 3X formula and combine it with local experience of what ATC normally will give to anticipate and plan ahead to avoid getting too high. This will minimize the need for speedbrakes. MCP SPEED or V/S is better than VNAV if you have to make last minute changes. This will avoid the rollercoaster that F/O discussed. VNAV tends to slow down early below 10.000 ft - many pilots will delay flaps until they have to slow down in order to fly a stabilized approach.

There will still be times when you have done everything right and ATC keeps you up high too long. As MLBWINGBORN wrote you can always adjust your rate of descent if you are a bit high. Simply lower the nose, increase you forward speed and rate of descent. You can do this up to the clacker. The problems start when you have turbulence and must stay around 280 or get an ATC speed restriction. That’s when you say unable or plan to extend gear a bit early or use speedbrakes.

The speed brake will only increase the rate of descent by about 6-700 fpm at 250 and 8-900 fpm at 280. On NG with winglets, the speedbrake is so inefficient that Boeing had to include gear extension in the QRH emergency descent checklist.

 

[Thedude]

I really wished that people would not refer to the speedbrake as the handle of shame. Its just another tool in your bag of tricks. Refering to it in such a negative manner will and does cause newbies in the right seat to be hesitant to use it and the might feel is if they have failed in some way. I work for a 727 operator and coming into DFW we get/ask for short appraoches all the time. Thats means we are on downwind a 10,000' and they want us to turn a five mile final over the dam at 210kts or greater. Sure no problem. Two way to do ....start getting configured at 10,000 or pull the brake and stay clean until you line up. We prefer to stay clean...it keeps the speed up (ATC loves that part) and you dont have the flaps out there vibrating like they are about to come off.
But then again,I will have to say nothing beats proper planning. Since we dont have V-nav, auto-throttles, or any of that advanced wizz-bang stuff we do a lot of mental mathmatics. It can get real intersting sometimes. Like going from SAT-LAX with no area-nav equip (no gps) and the auto-pilot won't stay engaged. I never was very good at math but I tell you I have become quicker on tabulating descent profiles.

 

[80/20]

Thedude - I agree 100% with what you say. Most of the postings on this thread lead to the same conclusion: As long as you make a genuine attempt to fly economically there is no shame in using the speedbrakes to handle unanticipated changes. What is a shame, is to stay up high too long at your own choice and routinely use the speedbrake to compensate for personal lack of planning at the expense of your airline.
Talking abut first generation jets, Thedude, “Nintendo kids” without your round dial background sometimes relies too much on the FMS. Computers are not too smart and you may end up way too high if you don’t back up with good old airmanship.

 

[MLBWINGBORN]

Man I wish the controllers in the JFK area
thought that anything over 500'fpm was gravy.

While they may not like 500 fpm..There is nothing wrong with it under most circumtances..

As long as you are complying with the clearance YOU excepted or any other restrictions they may have asked for its no big deal..

In a Boeing 737-700 its very rarely an issue..210 = 1100 to 1200 fpm..250 =1500 to 1600 at flight idle..

The only time I might push the issue of 500 fpm is after theyve dumped me early and asked for a continued descent..I will roll in 500 fpm in the MCP and adjust power for.74/300 until I get back on profile..

Other than that.. Its flight idle descent planning and the speed brakes only if I cant figure out another way of energy managment..

If the box and I are close..I will keep the descent required numbers cross checked all the way down with my math..

If ive done my job and its starting to look like ive got less outs than I started with..I wont bat an eye when I reach for the lever..

One of the benefits ive gotten from flying Lears in both the cargo and passenger business is both an appreciation for and dislike of speed brakes..
Passengers hated them and I didnt like the large pitch change/stick forces needed to deploy them smoothly..

Night cargo was a whole different world. The things we did with Lears still makes me smile..Popping the boards and dumping the gear high and close was normal procedure..
Swapping the flaps for the boards on schedule and spooling at 500 was a thing of magic to those sitting on the jumpseat..

The difference between the two is the required operation and the operating enviroment..
One tolerated the boards less than the other..

As for SWA..If im working hard and its just not working out..The boards are required and the guy next to me isnt gonna slap my hand..Period..

If im asleep at the switch and I need them because im being stupid..
Hes gonna say something because im not doing my job..Not because Ive reached for the boards..

Mike