737-700 vs 737-800

[Don Gato]

I have changed companies and started flying the -800 after a couple of years on the -700. Just completed my first flight on the 800 and felt is was a quite different bird in terms of handling. The approach was in windy conditions. Some of the things I noticed are that compared to the 700 the engines can hardly be heard, and the aircraft seems much more sensitive to control imputs. That besides the differences in performance Those are just first impressions since it was my first flight. I would appreciate it if any of you guys with experience on the type could point out some of the diferences you have found and tips on the 800. Thanks.

[Checkboard]

I flew the -700 on the line, however did a few sims in an -800 sim. The sim always had a siren-like whine when the gear came up (sounded a bit like an engine winding down :\ ). Is that actually the case with the aircraft? :confused:

[sudden Winds]

Hi,

1) takeoff and approach speeds are a bit faster as they are set by tail clearance margins (as per FCTM). For the same weight and of course same wing, flaps 30 speed is about 6 kts faster than that of a 700, and if you keep in mind that landing weights are naturally higher and as I said before, wing stays the same, you´ll realize you end up approaching at over 140 kts most of the time (with flaps 40!!)

Outer bug is no longer Vref 15 + 15 kts. It´s now Vref 15 + 20 kts. Single engine approaches when heavy are FAST.

Flap placard speeds are a bit different too. NG models have the same flap speeds, but in the 600 and 700 those are "artificially" reduced to increase service life.

2) A takeoff with flaps 1 in combination with an engine failure is an almost guaranteed tail strike. Tail clearance in that situation is 20 (real) centimeters. Otherwise, you got to try hard to make the tail kiss the rwy. Any normal takeoff at normal rotation rates with flaps 5 or 10 will give you at least 1 meter clearance. Most modern sims nowadays provide tail clearance information, so next time you fly the sim, ask your instructor what your tail clearance was. The other thing I try in the sim is a deliberate tail strike, and believe me, it ´s not that easy. You got to go for it.

3) fuel consumption. If you ever flew the 737-200, the fuel flow readings in the 800 will flash you back to the 200. Typical cruise is 1200 kg/hr per engine, as oppossed to 1000 in a rather heavy 700.

4) altitude capability. In a 700 you can go as high as 1200 ft above optimum FL, whereas in the 800 I never go any higher than 200 to 300 feet above optimum, especially in turbulent air.

5) we use it as category D, for approach. It requires 4 flight attendants (that depends on number of seats, i know). Standard Cat 7 for firefighting.

6) Different air conditioning system.

7) autothrottle takeoffs not allowed with EEC in ALTN in 26K engines or higher.

8) 2 overwing exits, strap attached to the aft one.

9) strengthened wing spars, landing gear and brakes.

Your comments about the handling characteristics sound much like what I felt when I first flew it. We operate both 7 and 8s.

And yes, the engines are a lot harder to hear. My first approach I really needed to look at the N1 readings a few times, not to overcontrol thrust.

There are more. If anyone disagrees with me please say so, I can always use someone else's knowledge and experience.
Rgds,
SW.

[Don Gato]

Thanks SW! Excellent information. Thanks for sharing.

[FlightPathOBN]

Sudden Winds,

I concur with the FAS, I see many pilots having difficulty with the 800 managing the energy on final.
There are also many RNP procedures that were designed for the NG, but wont work with the 800, the autopilot will disco a tight turn. It doesnt appear the FMS has kept up with the aircraft.

I have seen many aircraft, on final at 300 feet above the runway, doing 150kts, and literally doing everything they can between brakes and reverse (tearing up the runway I might add) to get it slowed down, even missing the high speed exit. (perhaps the reason for #9 above :bored:)
When I see speed brakes up to the flare, I know that has to be real interesting inside.

Boeing hasnt admitted to CAT D for the 800, perhaps that is a big part of the problem.

[Don Gato]

"I see many pilots having difficulty with the 800 managing the energy on final." Interesting. That was my feeling. The aircraft felt much more unstable than the 700 in a condition of gusty winds on final and flaps 40. I feel that a flaps 30 configuration would have been better on that scenario. Adding to that the unusual silent engine sound made things interesting :).

[FlightPathOBN]

Flaps 30 on final would require quite a bit of energy management, ie forethought, if one is used to other 737 variants.

Shes slick and heavy....use 2.8 GPA on final..3 degrees GPA is too much work.

Just so you are aware, I am not driving, I am just designing procedures and observing flight vals and wake turbulence.

[misd-agin]

Sudden winds -

#2 . Flaps 1 was primary takeoff flap. Tail strike awareness is a factor. No tail strikes, even with engine failures in the sim. Takeoff pitch reference line/attitude is your friend - 8 degrees of pitch until 10' RA, then increase at 3 degrees per second.

4. Most guys will fly 1000' under MAX ALT which is approx. 700' above OPT ALT. Next most common 'limit' is OPT ALT + 1000' (approx. MAX ALT -700')

Likes to float with Flaps 30. Will not float with Flaps 40. :ooh: You have to work really really hard to make it float with Flaps 40. Matter of fact, I've never seen it. Have experienced the dreaded 'oh xxxx' Flaps 40 impact. ;)

Airflow changes with Flaps 40 produces lateral flight control sensitivity changes. Roll input that raises the spoilers is shifted 3 (?) degrees sooner on one wing vs. the other wing. Takes a little bit to get used to, especially in crosswinds on short runways. :O

Nice hand flying airplane. Nice landing airplane. High speeds on final. :ok:

[FlightPathOBN]

Checkboard,

I think this is the siren like scream you were hearing...

http://sphotos.xx.fbcdn.net/hphotos-ash3/181094_10150889086488947_52514455_n.jpg

[sudden Winds]

Hi Misd Agin,

As far as I know, Boeing recommends the largest flap setting for the actual weight, to increase tail clearance, among others. We operate our 800s out of rather long runways and even at max passenger capacity, our surplus wt is normally huge. This means we use flaps 10 as a primary flap setting and we decrease it to 5 if performance limited, we then use 5 and bleeds off if performance is still a problem.

I understand boeing does not support two-step rotation techniques, like the one you mention, but it sounds like a good one.

Thank you for the contributions.

Regards,
SW.

[Denti]

With a normal 2,5°/sec rotation technique there is no real risk of a tailstrike, even in the simulator during that usual V1 cut. We use a boeing software and optimized take off settings which usually results in flaps 1 or sometimes 5, but we use up to 25 if needed.

Tailstrike risk is constantly assessed in out company via FOQA and actually the tail strike risk on both the 737-700 and -800 is extremely low. On the A320 and A319 the risk is pretty high though, but not on the A321 as pilots are much more aware of the long body length. However we did have a 737-800 tailstrike lately, the reason was performance calculated for the wrong weight, the classic thing, 57t instead of 75t.

[misd-agin]

Sudden winds - if Boeing recommended the highest possible flap setting almost every takeoff would be Flaps 15 or 20/25(depending upon individual company Ops Specs/SOP's).

The only time we didn't use Flaps 1 is if Flaps 5 allowed more weight for takeoff. If Flaps 5 didn't work we'd use Flaps 15.

At normal length runways I've never seen a 737NG takeoff with Flaps 15. It's typically F1 or F5.

Based on that I'd be surprised if Boeing recommended using the most flaps available. No U.S. airline appears to be doing that and neither are the foreign 737NG departures that I've observed.

[B-HKD]

Lets ask Boeing :ok:

http://www.boeing.com/commercial/aeromagazine/articles/qtr_1_07/AERO_Q107_article2.pdf

One of the prevention techniques mentioned:


"Consider use of greater flap setting to provide
additional tail clearance on some models."

I do recall seeing something very similar in the 744 FCOM.

misd-Agin: If something like the above is also written in the NG FCOM, I don't see why every operator would then stick to flaps25 departures on every NG takeoff only because Boeing "recommends" it.

Some 744 outfits only use flaps20, while others use both flaps10 and flaps20. In the end the higher flap setting is simply increasing the safety margin on something that is perfectly safe to do in the first place, as long as it is done properly.

I think its pretty clear. The recommendation (if indeed it exists for the NG) should definitely be taken into consideration for takeoffs during gusty considerations. Does this imply the greatest flap setting must be used for every other takeoff? nope.

[Don Gato]

B-HKD: Thanks for posting the Boeing article. Quite interesting! Thanks for the other posts also. Any other tips on flying the 800 vs the 700 are welcomed!

[misd-agin]

I understand boeing does not support two-step rotation techniques, like the one you mention, but it sounds like a good one.

It's not necessarily a two step process. Rotate using normal technique but do not exceed the takeoff pitch reference line that's on the HUD.

T.O. pitch reference line is at 8 degrees until 10' RA, at which point it increases (@ 3 degrees per second??) until V2 + additive logic takes over.

It you do not exceed the takeoff pitch reference(limit?) line you will not have a tailstrike.

[sudden Winds]

misd agin

The only time I used a HUD was during LOFT training in a sim and because I asked for it. We do not have HUDs installed in our planes.

Boeing does recommend largER flap settings but not necessarily the largest. We know what the advantages and disadvantages of very large flap settings are. What I am saying is that if you are not performance limited, in a 738, why would you use flaps 1, when 5 gives you increased tail clearance, lower v speeds and increased margin above stall speed, just to name a few. One large 738 operator, GOL Airlines, does that. They don´t conduct flaps 1 takeoffs at all, and if memory serves, from a conversation with one of their captains, they prioritize flaps 10 and move down to accomodate higher wts.

Regards,
sw.

[misd-agin]

We defaulted to the lowest flap setting. $$$$ Lower engine stress and fuel burn while accelerating to clean configuration. I think it actually defaulted to the lowest N1 setting, which typically was the lowest flap setting.

I don't think you get increased margin over stall speed. I think it's x percent above stall speed regardless of the flap setting.

You typically get improved climb performance in case of an engine failure.

Trading to increase one area penalizes another. Different companies stress different areas. We went for lower engine stress, less fuel, better climb performance, better initial s/e performance, at the expense of V speeds, runway used, and tail clearence on rotation.

[eagleflier]

Can someone please tell me what the best glide speed is on the 737 NG. I'm thinking it'd be the "up" bug or "best holding" speed from the FMC.

[sudden Winds]

Best Glide is flaps up speed, or Vref 40 plus 70 kts.

Of course lowest flap setting saves fuel, but a larger flap setting does provide a margin above stall, simply because you stall at a lower speed. good talking to you all.
sw.

[B-HKD]

Clean : V2 +20

Glide ratio on the NG is 22:1

[misd-agin]

Glide ratio of 22:1? Where'd you get that number from?

V2+20???? 24K motor, 140,000 lbs, Flaps 5 V2 approx. 145 kts. Flaps 15 V2 approx. 140 kts. Using your technique works out to 160-165 kts when the actual L/D glide speed is 211 (QRH).


Other techniques for computing basic L/D glide speed (actual speed is in the QRH for dual engine failure) -

GW + 70-75 kts (+75 light, +70 heavier) -
140,000 lbs + 70 = 210. QRH speed is 211.
120,000 + 75 = 195. QRH speed is 195.


Or Vref 30 + 65.

[FlightPathOBN]

For the most part, I see much more, and harder braking on the 800, simply that it is much easier and cheaper to cycle the brakes, than the engines...

Passengers get an E ticket ride on that landing...

Does a damn-damn on the runway of course.

[Sciolistes]

Glide ratio of 22:1? Where'd you get that number from?
Looks about right, I see around 1000 FPM at around 210 to 220 for the 800W.

[misd-agin]

Are you figuring out TAS? I came up with 19.5 (+/-).

787 was trying for 21:1. I think I read that it came it an 22:1.

I doubt the 737NG is as efficient as the 787.

Manual gives a distance estimate for a fixed altitude. That's 18:1, but it doesn't talk about what the maximum is.

[PPRuNeUser0190]

We fly both 700 & 800 and I personally like the 800 more. I feel in turbulent conditions on approach the 800 is less thrown around, more attitude stable.

Some differences in flying:
- descent planning: At usual descent weights the 800 will descent less fast than the 700 and correcting too much height is also more difficult in the 800. This has to do with the 800 having being heavier but having the same wing. If you look at a D-EAS curve a 700 doing 300kts in descent has more drag than an 800.

- flare: the 800 requires less flare than a 700. If you flare the 800 like a 700, you touch down 1000m into the runway :)

- be prepared for tailwind: be conservative when flying an approach with tailwind as the 800 does not slow down on approach with tailwind (config UP to F5).

[captplaystation]

If you fly an 800 with the short.field-performance kit fitted, intermediate appr gets a whole lot harder, as you will not have full ext on the LED's until F30.

My previous "best -friend" F10, is now useless, new "best-friend" is the LG which I am using a LOT earlier than in the "normal" 800's.