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msr001
6th Apr 2009, 09:11
Can anyone help me out here?
What is the best glide speed for the 737, what speed should you fly in case you lose both engines?
And how do you calculate alttitude lost vs ground distance covered in order to find out which airport is within range and which airport is just unachievable
I couldnt find that anywhere in B737-800 FCOMs and QRH (LOSS OF THRUST ON BOTH ENGINES) asumes that at least one engine is restarted...
Is it there some where and i missed it or is Boeing too optimistic?

Rainboe
6th Apr 2009, 15:53
Minimum speed flaps up- just above the minimum speed flaps up marker. Descent angle is approximately double idle engine descent angle, so max still air range from cruise likely to be about 60 miles. A 360 degree turn uses about 7000' altitude, aim to cross outer marker about double normal altitude, taking flap and gear as appropriate. Don't be low. Anything down to full flap if you are high. Full controls available right down to below Vref, use speedbrake if needed. Last resort is the traditional sideslip. Makes a real fun simulator session! Very few failures on it, almost everybody gets in. Furious mental calculations are needed though. Don't aim for long straight in- go for a base leg you can adjust.

rubik101
6th Apr 2009, 17:27
As mentioned, just above the green dot will be the best angle/range target. If they both stop, begin a gentle decent and get your buddy to find the nearest airport, straight road, open field, flat water, whatever.
Remember the Hudson!
As a further guide, if you can see a runway, you can land on it, provided it never goes much below the middle of your windscreen!
In the final stages of the approach, you can afford to be much higher than you would think possible. With gear down and 40 flap and no power at 140 kts, you will lose 1200-1400' a mile depending on weight. So get in close, make final configuration at about one mile and around 1300' but be ready to pull up hard at 200' to reduce the RoD. No harm in using speed brakes if the RoD reduces too much.
Keep your hand away from the Thrust levers! Keep it on the Speed Brakes.
Keep praying!

FCS Explorer
6th Apr 2009, 18:09
depending one your initial altitude you might wanna dive with around 320kts to improve your chances for a windmilling restart.
if no good:
FMS: set 2 miles final point to 1200ft (iso the usuall 600) adjust flaps according, keep gear up till ~200'

msr001
7th Apr 2009, 00:29
Thanks a lot guys some valuable info there....:ok:

That might just save so many lives one day but what really bugs me is the fact that these techniques are not mentioned anywhere in the training manual or the supplementry procedures..:ugh:

Which reverts us back to common sense and good airmanship.

SOPs doesnt fly planes; we do.

BelArgUSA
7th Apr 2009, 04:26
Minimum speed flaps up - as per Sir Rainbow mention above.
If you intend to glide with wings level, no turns, some 15-20 KIAS slower is ok.
Best L/D... You got a glider rating...?
xxx
:ok:
Happy contrails

BOAC
7th Apr 2009, 08:06
As a guide you can plan on twice the height in nm ie from 35000, 70nm. Best, however to try to find somewhere you can arrive overhead with space to plan some sort of 'circuit' to allow fine tuning, so knock off about 10-15nm as a ball park figure - if you can. As for gear at 200'....................:eek: I think your on your own, FCS.

framer
7th Apr 2009, 12:20
As for gear at 200'..

200' is too low if you want three greens. It will take a while, I would take gear at 1000ft at latest but thats just me....

scambuster
8th Apr 2009, 10:02
0.4 AoA will give you the best range regardless of IAS.

vikasdhariwal
8th Apr 2009, 10:05
Thanks a lot guys some valuable info there....http://static.pprune.org/images/smilies/thumbs.gif

That might just save so many lives one day but what really bugs me is the fact that these techniques are not mentioned anywhere in the training manual or the supplementry procedures..:ugh:

Which reverts us back to common sense and good airmanship.

SOPs doesnt fly planes; we do

vikasdhariwal
8th Apr 2009, 10:08
That might just save so many lives one day but what really bugs me is the fact that these techniques are not mentioned anywhere in the training manual or the supplementry procedures..:ugh:

Which reverts us back to common sense and good airmanship.

SOPs doesnt fly planes; we do.

16024
8th Apr 2009, 11:41
Lots of good stuff in the posts so far. It depends what you are trying to do.
You may be trying to glide the best distance (to reach an airport a long way away), or you may be trying to stay in the air as long as possible (to diagnose the problem, start the apu etc).
Best glide range will be at S/E driftdown speed which is in the manual, and also in the FMC, on the classic anyway. Just remember that as this will probably be below minimum clean, you will have to ignore normal flap speed schedule!
Minimum sink/best endurance speed will be about 0.2xV.S. below this,(ballpark 20 kts) but this is not in the books.
From trying it in the sim, I reckon a reasonable rule of thumb is: twice the height for estimating range, instead of normal three times. So from Fl200 you will get about 40Nm in a straight line.
Mike Sykes gives some excellent guidance on the Chris Brady website: Loss of thrust on both engines (http://www.b737.org.uk/lossofthrust.htm).

RAT 5
8th Apr 2009, 12:21
I haven't tried this yet, in the sim, but the idea of coming over head and flying a circuit, Hi key, Low key etc., seems best if possible. As for when on longer finals I would have thought at F5 aiming at the far end of the rwy would be good and then about 1000' agl lower gear and further flaps would bring the landing point closer to the normal end of the rwy. Do not aim at the normal TDZ point with only half the drag out. You'll get a big surprise when the dunlops dangle. If necessary assess the TDZ after the gear is down BEFORE lowering any more flap. That by itself may have brought the TDZ point to the closest allowable and any more drag will drop you in short. All this assuming the APU is running. If it's not there, then you have a seriously bad hair day.

framer
9th Apr 2009, 02:05
0.4 AoA will give you the best range regardless of IAS.


Can someone confirm that for us or elaborate a bit. It's been so many years since I looked at my aero's stuff that I've forgotten but it does sound right to me that there will be a min drag AOA that you can immediately set up on the EHSI.

I like the idea of putting a 5nm fix off the runway and a certain height on it (say 200/ 2500ft) and then sticking to that profile and start configuring like mad as you get to 5nm. This would only work of course if you were approaching the airport from the right direction and with enough height. This is quite likely though as there are often suitable airports underneath you somewhere well within glide range.

Can someone with access to a sim try 200kts/2500ft at 5nm to touch down and see what happens?

Framer.

Rainboe
9th Apr 2009, 12:01
I believe minimum drag speed is what the FMS would tell you to hold at clean, for any type- about a few knots below minimum flaps-up speed, therefore flaps-up speed is a good no-brainer. You have too many other things to work on!
The secret of these is to be close to your airport, don't try and head too far to one, especially upwind. Lose altitude in 360 degree turns keeping in mind you want to be starting final approach from a base position at a good altitude. Don't remain clean too late, you have to leave time for flaps and gear operating at slower speeds and have to anticipate the use of extra drag rather than react to the requirement.

They were really good to do in the sim- really woke you up! The Copilot would be told to stop trying to restart for training purposes and enjoy the ride. I think it would be a good detail to throw in every 3 years.

Checkboard
9th Apr 2009, 13:30
The following works in a gliding 737. Arrive over the outer marker (or 4 mile point) at twice the normal height (4 x 3 x two = 2400 ~ 2500 feet), flap five, gear up. Best to set the altitude alert to this height, and place the green descent arc over the point as you manoeuvre towards the airport. Once over this point select gear down, flap 15 and you will arrive at an easily controllable speed over the threshold.

My Company's training department worked out a full procedure in the sim, ran it in one of the sim rotations and has a two page brief on the procedure.

kenparry
9th Apr 2009, 17:16
That might just save so many lives one day but what really bugs me is the fact that these techniques are not mentioned anywhere in the training manual or the supplementry procedures..

Well: back in the 80s, the manuals from Boeing for the 737-200 which I was then flying had lots of general advice (not just QRH checklists) on non-normals, all subsequently removed. I believe this was at the behest of the Boeing lawyers, who claimed that the company could be sued if an event went sour after a crew followed the advice. For example, there was a long text on partial-gear landings, including (IIRC) figures for how far you might deviate from the centreline if you landed with one main gear locked up. The lawyers won their case - but did it improve safety? Not in my view.

president
8th Mar 2010, 18:18
so imagine an engine failure at 2000 feet, speed V2 + 20 (aprox 165 kts) and flaps 5. Which speed would give you the minimum angle of descent? I tried it in the sim and kept the flying speed at 165 until configuring for landing. Worked fine. But I could not get a clear answer to wether it would be better to fly 140 or maybe 180 kts (still in flap 5 config of course). Any ideas?


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