how high can you get in an approach on the 737
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From your post #13:
The point is that this limit does not define the RoD achieved at constant airspeed by a particular airplane, in a particular configuration, at a particular speed, at idle thrust.
The normal max in most airlines is 3000fpm within 3000' ft of MSA.
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Why would it need to?
Not only that but for every Unit of weight change the RoD will vary for any given config and speed. The amount of data in there is vast! And useless.
Not only that but for every Unit of weight change the RoD will vary for any given config and speed. The amount of data in there is vast! And useless.
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It doesn't need to because it has a different purpose. It is a manoeuvre limit that is not based on performance capability.
My understanding of the original question is that it is a performance question. Therefore the 'normal max in most airlines' is not a good basis for a reply.
If you want a simple rule-of-thumb, then JT's 1/1000 is hard to beat!
Here it is. The data points in the graphic are at 1 second interval, starting at 10h25m25.5s.
My understanding of the original question is that it is a performance question. Therefore the 'normal max in most airlines' is not a good basis for a reply.
If you want a simple rule-of-thumb, then JT's 1/1000 is hard to beat!
Originally Posted by BOAC
Show a plot at 27x1 second intervals and we can talk.
Last edited by HazelNuts39; 4th Aug 2013 at 13:02.
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Originally Posted by HN
If you want a simple rule-of-thumb, then JT's 1/1000 is hard to beat!
1) Add at least 20% (probably more) drag to go to full flap (40) from 'approach flap' ((? 5? ?15? )
2) Reduce speed from that speed (probably either 170 or 150) to Vref+5 (?130?)
Go back to your whizz-wheel and tell me what gradient you get - purely out of interest.
I cannot see rate of descent on your graph anywhere which is what I thought we were discussing.
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BOAC .. gradient suggested was for the -300.
Interestingly, I can't recall ever having had to dirty up at height in the 727-100/-200 to get down in normal ops.
Reasonably frequent need in the 737 if ATC had to hold you high back at 40-50 miles or so and then forgot about you for a while ...
Slow down to max flap speed in anticipation, dirty up on further descent clearance, go down, final slow down and into the slot .. worked very fine and was quite predictable.
One needed to factor in the wind, of course, and the mental arithmetic on a very long extremely tight straight in ILS saw steam coming out of the ears on the way down ... DME was king of the calculation inputs .. only very occasionally did one get caught out close in and still have to do an orbit or miss.
I recall one approach SY 16 ILS where we were still up near FL200 after coming around the corner at MQD onto the runway extended centreline .. and ATC just kept us there ... with a fairly high traffic density... lots of mental arithmetic until in the slot on the ILS but it worked out just fine.
Flap 25 was the most we were permitted to use without spinning up. Can't get that certification engineering hat off .. approach referring to last before land.
I was never really interested in ROD while poling (other than as a normal I/F scan input) unless the clearance required something specific .. it was all about gradient capability against requirement to end up wherever I needed to end up ...
Of course, I routinely ignored the FMS so still had enough grey matter in reserve to run the mental calcs .. had I tried to factor in the lies the box told about descent back in those days it would have been a foregone waste of time trying to make a tight descent requirement ....
Interestingly, I can't recall ever having had to dirty up at height in the 727-100/-200 to get down in normal ops.
Reasonably frequent need in the 737 if ATC had to hold you high back at 40-50 miles or so and then forgot about you for a while ...
Slow down to max flap speed in anticipation, dirty up on further descent clearance, go down, final slow down and into the slot .. worked very fine and was quite predictable.
One needed to factor in the wind, of course, and the mental arithmetic on a very long extremely tight straight in ILS saw steam coming out of the ears on the way down ... DME was king of the calculation inputs .. only very occasionally did one get caught out close in and still have to do an orbit or miss.
I recall one approach SY 16 ILS where we were still up near FL200 after coming around the corner at MQD onto the runway extended centreline .. and ATC just kept us there ... with a fairly high traffic density... lots of mental arithmetic until in the slot on the ILS but it worked out just fine.
Flap 25 was the most we were permitted to use without spinning up. Can't get that certification engineering hat off .. approach referring to last before land.
I was never really interested in ROD while poling (other than as a normal I/F scan input) unless the clearance required something specific .. it was all about gradient capability against requirement to end up wherever I needed to end up ...
Of course, I routinely ignored the FMS so still had enough grey matter in reserve to run the mental calcs .. had I tried to factor in the lies the box told about descent back in those days it would have been a foregone waste of time trying to make a tight descent requirement ....
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Originally Posted by BOAC
I cannot see rate of descent on your graph anywhere which is what I thought we were discussing.
The following graph shows for the 737-800 (NG) in the conditions of the accident:
A = actual rate of descent
B = loss of airspeed expressed as an equivalent rate of descent
A + B = the rate of descent achievable at constant airspeed
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Originally Posted by HN39 post#29
Therefore the 'normal max in most airlines' is not a good basis for a reply.
Now, if the mods will accept a diversion from the topic, I assume on your two plots that the timeline starts at the right hand end with CAS and RoD 'on spec' for an approach. Thus it presumably finishes at impact at the left hand end, with an actual RoD at impact of less than 400fpm, fully stalled, and a rate never exceeding 1000fpm (normal operating maximum) at any point?
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BOAC,
Not sure why you're asking and how much detail you are interested in, but:
I was looking for the longest interval where the engines were at idle (or almost) and the RoD and deceleration were approximately constant. The first 1 second interval starts at 10:25:25 and the last one ends at 10:25:48 (yes, from right to left in the two graphs). Impact was at about 10:26:01.5 at a RoD of about 3000 fpm. A few seconds prior to impact TOGA was selected and pitch control inputs were made.
Hope that answers your question.
Not sure why you're asking and how much detail you are interested in, but:
I was looking for the longest interval where the engines were at idle (or almost) and the RoD and deceleration were approximately constant. The first 1 second interval starts at 10:25:25 and the last one ends at 10:25:48 (yes, from right to left in the two graphs). Impact was at about 10:26:01.5 at a RoD of about 3000 fpm. A few seconds prior to impact TOGA was selected and pitch control inputs were made.
Hope that answers your question.
Last edited by HazelNuts39; 5th Aug 2013 at 13:02. Reason: typo
Only half a speed-brake
2: HzN / BOAC
I know this is not a 737, yet still:
(please ignore the unrealistic speed profile speed restrictions, I needed to set them up in order to avoid the SW's "out of envelope" warnings.)
Result (certified AFM data):
The first screen shows the init conditions for A320 with flaps 3 / SPD BRK etc.. and the second provides results for idle descent from 3000 to 1000 ft.
Cheers,
FD.
I know this is not a 737, yet still:
(please ignore the unrealistic speed profile speed restrictions, I needed to set them up in order to avoid the SW's "out of envelope" warnings.)
Result (certified AFM data):
The first screen shows the init conditions for A320 with flaps 3 / SPD BRK etc.. and the second provides results for idle descent from 3000 to 1000 ft.
Cheers,
FD.
Last edited by FlightDetent; 5th Aug 2013 at 22:27.
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The early 733 FMS descent profile was an exercise in fairytales for the little ones at night. I can't recall anyone who did other than ignore it other than for the TOD marker as a prompt for those too engrossed in their coffees.
Does the Airbus do it better in reality ?
Does the Airbus do it better in reality ?