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Chamonix
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Steep Approach:Which A/C Are Capable?

Fri Apr 15, 2011 8:49 pm

Steep approaches enable aircraft to approach paths at an angle of 5.5 degrees instead of the standard 3 degree at most airports.
Does anyone know which A/C are capable?
 
GBLKD
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RE: Steep Approach:Which A/C Are Capable?

Fri Apr 15, 2011 8:53 pm

Based on what I see going in and out of LCY

Dash 8
BAe 146/Avro RJ
Embraer 170
A318 (although IIRC BA's 2 are modified for the 5.5 degree approach)
And quite a few biz jets.
 
FlyASAGuy2005
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RE: Steep Approach:Which A/C Are Capable?

Fri Apr 15, 2011 11:41 pm

Quoting GBLKD (Reply 1):
And quite a few biz jets.



The CR2 seems to "nose-dive" naturally on final approach. I've been told it has to do with the degree of flats versus no leading edge slats. Another mentioned the "arm" location or the a/c.

Thoughts?
 
alasizon
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RE: Steep Approach:Which A/C Are Capable?

Sat Apr 16, 2011 12:20 am

I recall the Q400 is certified, and considering some of the flights I've been on, I could see it was possible.
 
aviopic
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RE: Steep Approach:Which A/C Are Capable?

Sat Apr 16, 2011 2:03 pm

Quoting Chamonix (Thread starter):
Does anyone know which A/C are capable?

I don't think that "capable" is the issue here, they probably all are.
Whether a manufacturer will do the certification is a matter of having enough customer interest.
 
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zeke
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RE: Steep Approach:Which A/C Are Capable?

Sun Apr 17, 2011 12:50 am

Quoting Aviopic (Reply 4):
I don't think that "capable" is the issue here, they probably all are.

Most larger jets would not be capable of a 5.5 degree approach, as to get certified for that sort of approach, you need to demonstrate intercepting the glide slope from above, which means a 7+ degree approach (around 1800 fpm @ 140 kt groundspeed).

Difficult in any aircraft.
 
Mir
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RE: Steep Approach:Which A/C Are Capable?

Sun Apr 17, 2011 2:19 am

Quoting FlyASAGuy2005 (Reply 2):
The CR2 seems to "nose-dive" naturally on final approach. I've been told it has to do with the degree of flats versus no leading edge slats.

This is true - if the CR2 had leading edge slats it have a much more typical attitude on final.

Quoting Aviopic (Reply 4):
I don't think that "capable" is the issue here, they probably all are.

I wouldn't bet on it. 5.5 degrees is very difficult to maintain in a stabilized fashion for a lot of aircraft.

-Mir
 
aviopic
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RE: Steep Approach:Which A/C Are Capable?

Sun Apr 17, 2011 10:35 am

Quoting zeke (Reply 5):
Most larger jets would not be capable of a 5.5 degree approach

Somehow my head isn't with larger a/c but it sounds logic though.  
Must be a function of mass.  


So I'll rephrase myself.
There are several a/c very well capable to perform a steep approach but not certified due to lack of customer interest.
For example Fokker certified both F50 and F70 but not F100 even though it never had a problem with LCY.

http://www.honders.net/tmp/F100LCY.jpg
 
Chamonix
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RE: Steep Approach:Which A/C Are Capable?

Sun Apr 17, 2011 7:42 pm

 
bj87
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RE: Steep Approach:Which A/C Are Capable?

Mon Apr 18, 2011 9:52 am

The Falcon 7X is certified for LCY.

And I am reasonably certain that the Falcon 900 and Global express are also certified for steep approaches.
 
Pihero
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RE: Steep Approach:Which A/C Are Capable?

Mon Apr 18, 2011 10:32 am

Quoting Mir (Reply 6):
Quoting FlyASAGuy2005 (Reply 2):
The CR2 seems to "nose-dive" naturally on final approach. I've been told it has to do with the degree of flats versus no leading edge slats.

This is true - if the CR2 had leading edge slats it have a much more typical attitude on final.

Careful here !
Due to its lack of leading edge device, the CRJ has a nose down attidude during normal approach at é 3° glide slope.
That negative attitude is going to be even morre accentuated with a 5.5) slope, i.e the flare has to be started earlier than a slat-equipped airplane, which is a disadvantage.

Quoting GBLKD (Reply 1):
0
A318 (although IIRC BA's 2 are modified for the 5.5 degree approach)

It's mainly a matter of software change when the "Steep 3ppraoch3 button is depressed . The most visible aspect is the extension of spoilers # 3 and 4 to 30° [b]with speddbrake lever Full[/] and a change in the flare mode to cope with the higher v/s and attitude rotation.
 
Chamonix
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RE: Steep Approach:Which A/C Are Capable?

Mon Apr 18, 2011 11:25 am

Is the G650 steep approach certified?
 
tdscanuck
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RE: Steep Approach:Which A/C Are Capable?

Mon Apr 18, 2011 1:49 pm

Quoting Aviopic (Reply 4):
I don't think that "capable" is the issue here, they probably all are.

Not really...in order to descent that steeply you need to be able to shed enough energy to stay on the glidepath without accelerating. The steeper the glidepath, assuming roughly equal approach speeds, the more energy you need to be able to shed. The FAR requirement for steep descents isn't as high as 5.5, so not all aircraft are capable of or designed to dump energy (via drag) that quickly.

Tom.
 
DiamondFlyer
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RE: Steep Approach:Which A/C Are Capable?

Mon Apr 18, 2011 2:37 pm

Quoting Chamonix (Reply 11):
Is the G650 steep approach certified?

Seeing as the G650 isn't certificated yet, I don't think that i could be certified for steep approaches.

-DiamondFlyer
 
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Asturias
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RE: Steep Approach:Which A/C Are Capable?

Tue Apr 19, 2011 12:15 am

I'm pretty sure that the F-50 is capable of a 5.5° glide slope approach. Can't be sure, since I wasn't in the cockpit (just pax) but whoa nelly, did she dive at approach.

I was sliding forward in my seat. That doesn't happen at 3° I think.

asturias
 
Pihero
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RE: Steep Approach:Which A/C Are Capable?

Tue Apr 19, 2011 12:30 am

Quoting Asturias (Reply 14):
I'm pretty sure that the F-50 is capable of a 5.5° glide slope approach.

Propeller airplanes shouldn't have a problem doing steep approaches : the props can be very effective air brakes.
In the same vein, jetliners which have speedbrakes (as opposed to *spoilers* ) have the capability : the Fokker jets, the Avros...etc...
I do not know the Embraer solution (though I'm mighty interested ) because I don't think it"s draggy enough without speedbrakes, and I don't see on the available pictures the A318 solution of partial spoilers extension.
 
aviopic
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RE: Steep Approach:Which A/C Are Capable?

Tue Apr 19, 2011 10:13 am

Quoting Pihero (Reply 10):
Due to its lack of leading edge device, the CRJ has a nose down attidude during normal approach at é 3° glide slope.

Are you sure there is a relation between the two ?
I don't know but the F70/100 doesn't have slats either but as far as I am aware not a nose down attitude during approach.

Quoting tdscanuck (Reply 12):
Not really..

Thanks, earlier posts already corrected my naive assumptions.

Quoting Asturias (Reply 14):
I'm pretty sure that the F-50 is capable of a 5.5° glide slope approach.

See reply 7
Quoting Aviopic (Reply 7):
For example Fokker certified both F50 and F70 but not F100
Quoting Pihero (Reply 15):
Propeller airplanes shouldn't have a problem doing steep approaches : the props can be very effective air brakes.

Even "very effective" is an understatement for some a/c.
The steepest approach I've done(not as pilot) is straight down in a Pilatus Porter from flight level 140 to less than 1000ft. Even in this 90 degree down attitude the airspeed remains a steady 150kts.
 
Pihero
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RE: Steep Approach:Which A/C Are Capable?

Tue Apr 19, 2011 11:57 am

Quoting Aviopic (Reply 16):
Quoting Pihero (Reply 10):
Due to its lack of leading edge device, the CRJ has a nose down attidude during normal approach at é 3° glide slope.

Are you sure there is a relation between the two ?
I don't know but the F70/100 doesn't have slats either but as far as I am aware not a nose down attitude during approach.

Yes, I am.
The Fokker has the wing set at a slightly negative angle relative to the fuselage, hence its slightly nose-up attitude in the approach, and a marked higher attitude in the cruise.
 
bond007
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RE: Steep Approach:Which A/C Are Capable?

Tue Apr 19, 2011 2:09 pm

Quoting Pihero (Reply 17):
Yes, I am.

Actually you just showed that it isn't simply the lack of slats, but also a factor of wing angle. Otherwise all aircraft without leading edge slats would have a different approach attitude ... which you explained they didn't.


Jimbo

[Edited 2011-04-19 07:13:12]
 
Pihero
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RE: Steep Approach:Which A/C Are Capable?

Tue Apr 19, 2011 4:05 pm

No, you're wrong.
A wing set at too shallow an angle will have a marked nose-up attitude in cruise, which is not comfortable for the passengers and hell for the cabin crew. Could be ok for shorter flights, though.
There is also an influence of the flap technology : Fowler types extend the chord of the wing, somehow lessening the nose-down attitude, but it's still there as these pics show :

Best way to identify a DC-8 from a 707 ?

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Photo © Udo K. Haafke


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Photo © Manny Gonzalez - Thrust Images



Some airplanes down memory lane :
The caravelle,
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Photo © Pierre Mouhot



The One-eleven,
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Photo © Ad Vercruijsse



The Comet :
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Photo © Peter Seemann

 
bond007
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RE: Steep Approach:Which A/C Are Capable?

Tue Apr 19, 2011 4:46 pm

Quoting Pihero (Reply 19):
No, you're wrong.

I simply said what you explained, so I can't be wrong!

If you agree that the Fokker 70/100 doesn't have a marked nose down attitude on approach, then it isn't simply a lack of slats that causes the CRJ to seem nose down, but also a factor of wing angle. If the CRJ had a more negative wing angle, it would not fly so nose-down on approach (but more nose-up in cruise of course).


Jimbo
 
mandala499
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RE: Steep Approach:Which A/C Are Capable?

Tue Apr 19, 2011 5:25 pm

Quoting Pihero (Reply 15):
I do not know the Embraer solution (though I'm mighty interested ) because I don't think it"s draggy enough without speedbrakes, and I don't see on the available pictures the A318 solution of partial spoilers extension.

The videos are available for the Embraers and the 318s in the partial spoiler extension solution in youtube...

But... here's a sneak peek...

View Large View Medium
Click here for bigger photo!

Photo © Ruud Brinks


(note: outboard ailerons are neutral, outer spoiler isn't!)

Ah heck... here's the Embraer one....
http://www.youtube.com/watch?v=lmXiwKWU3N4
Nice play of the spoiler mixer in the partial extension steep approach mode... and a go-around! 

And this is the A318 one...
http://www.youtube.com/watch?v=Aho_BWx7OR4

The E170 was originally designed to have a ventral speedbrake (under the belly), but I think the partial extension is an easier method...

Mandala499
 
Pihero
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RE: Steep Approach:Which A/C Are Capable?

Tue Apr 19, 2011 5:43 pm

There area few concepts that define a wing ; among them,
An airfoil, and the line that joins the leading edge to the trailing edge which is called a chord.
That is rather important as it's the angle between the chord and the airflow that defines the angle of attack of the wing..
Now suppose the wing is set at 0° angle relative to the fuselage.
1/- when the flaps are deployed in the absence of leading edge devices, the new chord has a very markedly increased AoA that would generate a lot of lift and drag, too.
In order to follow an approach-to-land glide path, that aircraft will have a nose-down attitude
2/- The same wing, this time equipped with some leading edge devices, will in fact show a lower AoA with everything deployed, may be even a negative one, corrected with a - again - marked nose-up attitude in the approach.
Now you can argue all you want, the pictures I posted are quite demonstrative of the relationship LE devices / approach attitude.
Of course, there will be instances when the phenomenon doesn't show a lot (a heavy aircraft would present less of a nose-down attitude ) but it is there, whether you like it or not.
As for the angle the wing is set at, one of the reasons that define it is takeoff and landing geometry : one of the parameters could be the Vlof demonstration : too much of a set angle --> too much drag and a lousy Vlof.
As it is not a long hauler, that slope in the cabin doesn't hurt too much.
 
Pihero
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RE: Steep Approach:Which A/C Are Capable?

Tue Apr 19, 2011 5:57 pm

Quoting mandala499 (Reply 21):
But... here's a sneak peek...

Thanks, A problem and one solution for both brands? and probably equivalent software tweaks as the spoiler extension comes long before complete HLD extension for both airplanes.
Beautiful video
Can't wait for the Salon !

Cheers !
 
mandala499
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RE: Steep Approach:Which A/C Are Capable?

Tue Apr 19, 2011 8:48 pm

Quoting Pihero (Reply 23):
A problem and one solution for both brands? and probably equivalent software tweaks as the spoiler extension comes long before complete HLD extension for both airplanes.

Yes, both brands have spoilers-by-wire, hence the software tweak is possible.
I was, ironically, hoping that Embraer would use the dorsal speedbrake concept for the steep approaches... I'm rather disappointed with the outcome method chosen, albeit pleased with the desired result... simplicity...

Quoting Aviopic (Reply 16):
I don't know but the F70/100 doesn't have slats either but as far as I am aware not a nose down attitude during approach.

If you see an F70/100 on a full flaps approach and not too heavy, it goes nose down by a very noticeable amount. With less than full flaps (for long runways and fast approaches at busy airports), you won't see much of a nose down attitude, heck, it might come up with a nose up instead! Such is the amazing Fokker wings!   

Quoting Pihero (Reply 23):
Can't wait for the Salon !

Planning for it will start in 2 weeks...   
 
liedetectors
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RE: Steep Approach:Which A/C Are Capable?

Tue Apr 19, 2011 10:35 pm

Quoting Chamonix (Reply 11):
Is the G650 steep approach certified?

No, but the G150 is.
 
saab2000
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RE: Steep Approach:Which A/C Are Capable?

Wed Apr 20, 2011 2:28 pm

You guys are forgetting the SAAB 2000. It was designed with LCY and LUG in mind. I used to fly to both of those places (was based in LUG) and we did these steep approaches all the time. The LCY was 5.5º IIRC (as someone else mentioned) but the G/S in LUG was 6.67º. The difference is that the approach in LUG was an IGS and we were not allowed to couple to the glide slope, it was for 'reference only'. It was essentially a localizer approach with the PAPI being at 4º, meaning we had to dive from the 6.67º slope to visually fly the last few miles at 4º, meaning we did nose down pitches in excess of 15º on a regular basis.

Not an approach for the faint of heart.
 
imiakhtar
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RE: Steep Approach:Which A/C Are Capable?

Wed Apr 20, 2011 3:38 pm

Quoting saab2000 (Reply 26):
It was essentially a localizer approach with the PAPI being at 4º, meaning we had to dive from the 6.67º slope to visually fly the last few miles at 4º, meaning we did nose down pitches in excess of 15º on a regular basis.


Wow! Cool stuff. Must have been interesting with the winds rolling off the local terrain too. My cousin used to live in Lamone on the approach to rwy19. When I visited I used to climb the hills to watch the circling approaches.
 
Pihero
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RE: Steep Approach:Which A/C Are Capable?

Mon Apr 25, 2011 8:53 am

Can't help but post this outstanding picture in this thread.
A good demonstration of what we've been talking about and the influence of leading-edge devices to approach attitudes.

View Large View Medium
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Photo © Ben Wang

 
PGNCS
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RE: Steep Approach:Which A/C Are Capable?

Mon Apr 25, 2011 3:30 pm

Quoting Aviopic (Reply 16):
Quoting Pihero (Reply 10):
Due to its lack of leading edge device, the CRJ has a nose down attidude during normal approach at é 3° glide slope.

Are you sure there is a relation between the two ?

Yes.

Quoting Pihero (Reply 28):
Can't help but post this outstanding picture in this thread.
A good demonstration of what we've been talking about and the influence of leading-edge devices to approach attitudes.

Good and classic picture, Pihero. All other things being equal, an aircraft without leading edge devices will be more nose low on approach than one with slats (or LE flaps.) The CRJ family demonstrates this, but so does the DC-9-10 (no slats) versus the rest of the family. The -10 is notably nose low on approach, while the other variants are slightly nose high to varying degrees.
 
Aircellist
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RE: Steep Approach:Which A/C Are Capable?

Mon Apr 25, 2011 8:12 pm

I saw the picture on the general page and I thought: "Should add it to the discussion about steep approach!..."!

Late by half a day!
 
Mir
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RE: Steep Approach:Which A/C Are Capable?

Mon Apr 25, 2011 9:14 pm

Quoting DiamondFlyer (Reply 13):
Seeing as the G650 isn't certificated yet, I don't think that i could be certified for steep approaches.

And seeing as the G550 isn't approved for LCY, I find it hard to imagine that the G650 would be.

-Mir
 
Chamonix
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RE: Steep Approach:Which A/C Are Capable?

Tue Apr 26, 2011 6:03 am

Thus the Falcon 7x has the edge over the G650 as the former is certified for steep landings as opposed to the latter?
 
Mir
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RE: Steep Approach:Which A/C Are Capable?

Tue Apr 26, 2011 6:27 am

Quoting Chamonix (Reply 32):
Thus the Falcon 7x has the edge over the G650 as the former is certified for steep landings as opposed to the latter?

In that particular area, yes. That doesn't in itself make the 7X a better plane - the G650 (and G550) have other advantages over the 7X. Like pretty much everything else in aviation, it's a tradeoff.

-Mir
 
Clydenairways
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RE: Steep Approach:Which A/C Are Capable?

Wed Apr 27, 2011 2:07 pm

I didn't see the Dash 7 mentioned yet.

Before London City Airport was built, Capt Harry Gee landed a Dash 7 on Heron Quays to demonstrate the capabilities of the aeroplane.

here is a link to a video of the landing on the quay in 1982
http://www.lcacc.org/history/heron.WMV

Also note when the airport opened in 1987 the runway was much shorter than it is today, and it also had a 7.5deg glidepath angle at that time. Only the Dash 7 and the D228 were approved to operate in there.

The Dash 7 was a real Steep approach airliner.



I think one or two posters here got Steep Approach and Aircraft landing with nose down attitude mixed up. But Mr Pihero has clarified this perfectly.
 
aviopic
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RE: Steep Approach:Which A/C Are Capable?

Wed Apr 27, 2011 6:22 pm

Quoting Pihero (Reply 28):

Can't help but post this outstanding picture in this thread.
A good demonstration of what we've been talking about and the influence of leading-edge devices to approach attitudes.

I have absolutely no problem with your theory and you are probably right.
The picture tells me nothing though as the database probably holds just as much photos showing the opposite.
Like Mandala already said the Fokkers approach can be in any shape you want as a function of airspeed which is controlled by elevator.
Go fast, pitch goes up. Go slow, pitch goes down.


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Photo © Johannes Ehlen



Correct airspeed = flat as a pancake  
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Photo © Tommy Desmet
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Photo © Thomas Posch - VAP

 
Pihero
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RE: Steep Approach:Which A/C Are Capable?

Wed Apr 27, 2011 10:38 pm

Quoting Aviopic (Reply 35):
Like Mandala already said the Fokkers approach can be in any shape you want as a function of airspeed which is controlled by elevator.

That"s NOT AT ALL what Mandala said, especially the following assumption that's completely wrong on an approach during which the glideslope is pretty much fixed.:

Quoting Aviopic (Reply 35):
Go fast, pitch goes up. Go slow, pitch goes down.

In this case, the faster you fly, the steeper the nose-down attitude, with a given flap setting.
 
aviopic
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RE: Steep Approach:Which A/C Are Capable?

Thu Apr 28, 2011 6:26 am

Quoting Pihero (Reply 36):
especially the following assumption that's completely wrong on an approach during which the glideslope is pretty much fixed.:

I am sorry but that's how the autopilot works during descend.

Quoting Pihero (Reply 36):
In this case, the faster you fly, the steeper the nose-down attitude

Nope, the other way around as the elevator is controlling pitch to a fixed speed.
 
David L
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RE: Steep Approach:Which A/C Are Capable?

Thu Apr 28, 2011 11:20 am

Quoting Aviopic (Reply 37):
I am sorry but that's how the autopilot works during descend

If you control your airspeed in the descent using only the elevators, you will also change your flightpath. It might be OK during the descent but it's probably not something you want to be doing during the landing phase, when maintaining a suitable airspeed and a fixed flightpath (i.e. the glideslope) are required.

I think the point is that an increase in speed will increase lift so will require a more nose-down attitude in order to remain centred on the glideslope.
 
mandala499
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RE: Steep Approach:Which A/C Are Capable?

Thu Apr 28, 2011 12:00 pm

Quoting Aviopic (Reply 35):
Like Mandala already said the Fokkers approach can be in any shape you want as a function of airspeed which is controlled by elevator.
Go fast, pitch goes up. Go slow, pitch goes down.

HOLD ON JUST RIGHT THERE Meneer!
I said:

Quoting mandala499 (Reply 24):
If you see an F70/100 on a full flaps approach and not too heavy, it goes nose down by a very noticeable amount. With less than full flaps (for long runways and fast approaches at busy airports), you won't see much of a nose down attitude, heck, it might come up with a nose up instead!

For: Go fast, pitch goes up. Go slow, pitch goes down
Correct, but that is on a free path basis. For a given trim/elevator setting... go fast, pitch goes up AND flight path goes up. Go slow, pitch goes down and flight path goes down.

Now, Let's keep it simple... Slap on the autopilot to maintain a certain altitude (a level flight path)... at a certain speed.
Increase the speed, your pitch angle will go down/reduce. Decrease your speed, your pitch angle will go up/increase.
 
aviopic
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RE: Steep Approach:Which A/C Are Capable?

Thu Apr 28, 2011 1:03 pm

Quoting David L (Reply 38):
If you control your airspeed in the descent using only the elevators, you will also change your flightpath. It might be OK during the descent but it's probably not something you want to be doing during the landing phase, when maintaining a suitable airspeed and a fixed flightpath (i.e. the glideslope) are required.

And yet this is how the AP does it's job during descent, approach and landing(on F70/100 anyway).
Airspeed is controlled by elevator(pitch) and vertical speed is controlled by thrust, together they keep track of flightpath/ILS.

Quoting mandala499 (Reply 39):
For: Go fast, pitch goes up. Go slow, pitch goes down
Correct, but that is on a free path basis.

I was not talking about a free path but a normal ILS approach flown on AP as usually happens.

Quoting mandala499 (Reply 39):
Now, Let's keep it simple... Slap on the autopilot to maintain a certain altitude (a level flight path)... at a certain speed.
Increase the speed, your pitch angle will go down/reduce. Decrease your speed, your pitch angle will go up/increase.

Like I did not disagree with the initial "nose up" "nose down" theory this one is also perfectly ok.
The thread however is about steep approach and not level flight.
 
David L
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RE: Steep Approach:Which A/C Are Capable?

Thu Apr 28, 2011 1:31 pm

Quoting Aviopic (Reply 40):
And yet this is how the AP does it's job during descent, approach and landing(on F70/100 anyway).
Airspeed is controlled by elevator(pitch) and vertical speed is controlled by thrust, together they keep track of flightpath/ILS.

If the speed increases, the lift increases. If you are trying to stay centred on the ILS, you will need to lower the nose to stay on the glideslope, otherwise you'll drift above it. In practice, the (auto)pilot will adjust attitude and thrust, if necessary, to maintain an appropriate speed while staying on the glideslope.

The basic point that an increase in speed will require a nose-down adjustment in order to stay centered on the glideslope is all down to physics.

Quoting Aviopic (Reply 40):
The thread however is about steep approach and not level flight.

Level flight or steep approach, it's all the same in this context. We're talking about maintaining a fixed flightpath.
 
mandala499
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RE: Steep Approach:Which A/C Are Capable?

Thu Apr 28, 2011 4:30 pm

Quoting Aviopic (Reply 40):
The thread however is about steep approach and not level flight.

What I said is valid for a set flight path angle value. So, instead of putting an FPA of 0.0, put it to -3.3 or -5.5 degrees... and the same principles apply. Increase the speed, the A/P will move the pitch angle down to keep the aircraft on the set FPA... reduce the speed, the A/P will move the pitch angle up to keep the aircraft on the set FPA.
So, instead of Go fast, pitch goes up. Go slow, pitch goes down when maintaining a fixed FPA, it is the other way around!

And then, give the same set of speed, flaps setting and FPA, the heavier you are, the higher the nose up (or less nose down), and the lighter you are, the less nose up (or more nose down).

This is valid on whether you have the leading edge slats or not, whether you have flaps or not...

Mandala499
 
Chamonix
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RE: Steep Approach:Which A/C Are Capable?

Thu Apr 28, 2011 5:01 pm

Quoting mandala499 (Reply 42):
So, instead of putting an FPA of 0.0, put it to -3.3 or -5.5 degrees.

Does that mean that FPAs are unbridled and any ° can be inputted regardess if it is steep approach capable or not.
In other words,can one force a steep approach?

[Edited 2011-04-28 10:05:16]
 
aviopic
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RE: Steep Approach:Which A/C Are Capable?

Thu Apr 28, 2011 5:27 pm

Quoting David L (Reply 41):
Level flight or steep approach, it's all the same in this context. We're talking about maintaining a fixed flightpath.

Yes, from an AP control law viewpoint it is only the opposite.  
Quoting mandala499 (Reply 42):
So, instead of Go fast, pitch goes up. Go slow, pitch goes down when maintaining a fixed FPA, it is the other way around!

I get the feeling we are telling the exact same thing just from a different starting point.  
Quoting mandala499 (Reply 42):
Increase the speed, the A/P will move the pitch angle down to keep the aircraft on the set FPA... reduce the speed, the A/P will move the pitch angle up to keep the aircraft on the set FPA.

In the context of an approach(fixed FPA(ILS) and speed) Go Fast means Pitch Up to reduce speed as speed in this instance is controlled by elevator.
Go Slow means Pitch Down to increase speed due to the same control law as above.
Obviously both seen from an AP viewpoint as I tried to indicate by supplying photo examples.


Which in my view is why not many spotters/photographers will see a pitch down approach as predicted by the theory of missing slats which in it self is probably right(as mentioned over and over again).
 
Pihero
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RE: Steep Approach:Which A/C Are Capable?

Thu Apr 28, 2011 6:23 pm

You're not helping your case at all and your premiuces are dead wrong
In a free descent - whether it's called *OPEN DESC* or *FLCH*, you are right : The pitch control effectively controls the IAS.
That is all, and there is no "This is how the PA works", because it is not, once you want to follow a given flight path.
Aerodynamics are there and rule the air !

They say that, for a given set of flight parameters -i.e speed and flight path - there are two possible pairs of speed and thrust settings : each one on either side of the necessary thrust/power curve (as you like it ). Some call that equation the Fn./Fa curve where Fn is the thrust needed for that particular phase of flight and Fa the available thrust.
Of course the choice is in fact reduced to only one pair as the other one is inside what we call the 2nd regime, close to high AoAs, therefore uncomfortable.
What a pilot does -without really a conscient thought- and what a PA does is in fact making real that pair of necessity : adapt the airplane trajectory with an engine thrust / power and a speed. It is only then, and for small corrections only that your "pitch controlled speed" could be seen.
But to say that is the basis of Fokker's autopilot technology is totally untrue.
The Dutch haven't re-invented flight mechanics, I'm afraid.

[Edited 2011-04-28 11:27:49]
 
mandala499
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RE: Steep Approach:Which A/C Are Capable?

Thu Apr 28, 2011 7:55 pm

Quoting Chamonix (Reply 43):
Does that mean that FPAs are unbridled and any ° can be inputted regardess if it is steep approach capable or not.
In other words,can one force a steep approach?

Yes, one can... doesn't mean that one should!

Quoting Aviopic (Reply 44):
I get the feeling we are telling the exact same thing just from a different starting point.

Well... let's try for the following JUST IN CASE THIS IS A LANGUAGE/PERCEPTION PROBLEM:
What would have a more nose up (in other words, less nose down) pitch angle:
A320 passing 3000ft at 55Tons on full flaps, gear down, Wind 0KTS, Temp ISA, FPA -3.3 and Speed Selected is 130KTS; or
A320 passing 3000ft at 55Tons on full flaps, gear down, Wind 0KTS, Temp ISA, FPA -3.3 and Speed Selected is 160KTS

One answer would conclude that the problem is in language, the other would conclude that there is a flaw in your understanding on flight path control on the pitch axis...

Mandala499
 
aviopic
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RE: Steep Approach:Which A/C Are Capable?

Thu Apr 28, 2011 9:13 pm

Quoting Pihero (Reply 45):
You're not helping your case at all

It's not "my" case.

Quoting Pihero (Reply 45):
your premiuces are dead wrong

You make it sound like my life is at steak.
Well I got news for you, it ain't  
Quoting Pihero (Reply 45):
The Dutch haven't re-invented flight mechanics, I'm afraid.

I've checked all posts again but fail to see any indication of a new invention, let alone a Dutch invention.
I am afraid your anti Dutch feelings are getting in the way as in the civil thread.
Please relax, there is no enemy behind every tree.
In fact nobody, repeat nobody denied your theory.
The fact that there are relative few F70/100 approach photos with a nose down attitude in contrast with the missing slat theory remains though which was my point to begin with.


This is all effort I'll put into this.
Some of us have an actual job and simply no time to go on and on................ like in the mentioned civil thread.
I am not going there, sorry.

Have fun without me though,
Cheers

  
 
Pihero
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RE: Steep Approach:Which A/C Are Capable?

Thu Apr 28, 2011 9:46 pm

It would have been so much simpler to acknowledge that one has made a mistake.
And that Fokker hasn't re-invented a new autopilot software based on new aerodynamics research and flight control development.
But when I think that kind of theory is being taught to students in avionics courses, I shudder.
Just my   
 
Chamonix
Topic Author
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RE: Steep Approach:Which A/C Are Capable?

Thu Apr 28, 2011 10:10 pm

Aviopic:
Having read all the threads,there is no anti-Dutch resentment or otherwise!
Absolutely no racisim intended by anyone!
As English is is not your Mother-tongue ,its labyrinthine subtleties and inverted innuendo are hard to fathom.
I am sorry that you feel offended but do not be!
Chamonix

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