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I have no idea about C-17s, but I wonder if the fact that Navy dudes flying an AOA approach vice just a specific airspeed have anything to do with it? That’s a random guess considering you said there’s such a pitch issue with the MD-11

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17 minutes ago, SocialD said:

Don't most Air Force aircraft fly AOA? 

Nope.  

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1 hour ago, SocialD said:

Don't most Air Force aircraft fly AOA? 

Every fighter I have flown or evaluated used AOA, but all, with the exception of the Super Hornet and Hornet, were flown in the region of "normal command" (front side) which is more intuitive to fly, IMO.

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2 hours ago, Muscle2002 said:

Every fighter I have flown or evaluated used AOA, but all, with the exception of the Super Hornet and Hornet, were flown in the region of "normal command" (front side) which is more intuitive to fly, IMO.

I'm very surprised by this statement.  Notwithstanding those two jets, the others all flew approaches faster than L/Dmax?  

I think there is something I'm missing.  

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Posted (edited)
3 hours ago, HuggyU2 said:

I'm very surprised by this statement.  Notwithstanding those two jets, the others all flew approaches faster than L/Dmax?  

I think there is something I'm missing.  

These AoA are likely very close to L/Dmax, but I imagine that in each aircraft, test teams built in a pad to ensure acceptable handling qualities were maintained. This would be to protect against moving in-and-out of backside and frontside regimes. That said, none of the flight manuals I have read corroborate such a hunch, but I know that in evaluating "Steady-state flight-path response to pitch controller," the MIL-STD evaluation criteria requires that an "aircraft remains tractable at commonly encountered off-nominal speeds." In this case, off-nominal is 5 knots slow. Given that airspeed behavior becomes unstable at speeds below minimum drag speed, and that L/Dmax occurs at Dmin, it makes sense to build in a buffer, landing performance notwithstanding, and thus, published flight manual approach speeds are above L/Dmax. 

Edited by Muscle2002
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Posted (edited)
7 hours ago, Muscle2002 said:

Every fighter I have flown or evaluated used AOA, but all, with the exception of the Super Hornet and Hornet, were flown in the region of "normal command" (front side) which is more intuitive to fly, IMO.

Do you mean have an AOA gage in the cockpit for reference, or fly an actual AOA approach? There's a difference.

Edited by Bigred

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Do you mean have an AOA gage in the cockpit for reference, or fly an actual AOA approach? There's a difference.
Even the KC-135 has AOA gauges for both pilots. They aren't the most precise instruments in the world, but can be used in the event of a dual ADC failure (chances of that = slim to none). There is an arc at approach speed (.6 AOA). 1.0 units is stall. You really don't need airspeed or AOA to get the thing on the ground anyway. Known pitch and power settings along with an infamous full-flap burble will get you within 5 knots of approach speed every time.

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Posted (edited)
16 hours ago, Muscle2002 said:

 Given that airspeed behavior becomes unstable at speeds below minimum drag speed, and that L/Dmax occurs at Dmin, it makes sense to build in a buffer, landing performance notwithstanding, and thus, published flight manual approach speeds are above L/Dmax. 

I'm not a test pilot.  However, I have a fair amount of experience in a multitude of military powered-aircraft and can't think of one I've flown where this is the case.  

I've got about 6 sorties in the F-16, including a front seat flight where we did SFO's.  Although it has been 10 years... and everything is done primarily in AoA... I recall that approach speeds were ~150 KIAS and L/Dmax is 200 KIAS... which puts it in the same category as the Hornet / Super Hornet you mention above.  

Again, I'm sure I'm missing something.  Can you give some examples of military powered-airplanes where approach speed is above L/Dmax?

Edited by HuggyU2

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8 hours ago, Gazmo said:
18 hours ago, Bigred said:
Do you mean have an AOA gage in the cockpit for reference, or fly an actual AOA approach? There's a difference.

Even the KC-135 has AOA gauges for both pilots. They aren't the most precise instruments in the world, but can be used in the event of a dual ADC failure (chances of that = slim to none). There is an arc at approach speed (.6 AOA). 1.0 units is stall. You really don't need airspeed or AOA to get the thing on the ground anyway. Known pitch and power settings along with an infamous full-flap burble will get you within 5 knots of approach speed every time.

I guess I wasn’t too clear. I’m tracking most every military plane has some sort of AOA gage. My point is that, using the 135 as an example, I may fly an approach at 165kts and reference the AOA gage, but I’m not slaved to what it says precisely, I’m more concerned with airspeed.

In comparison, Navy guys fly a specific AOA all the way to the deck. Airspeed is important but AOA even more so since they don’t flare.

I’m sure the MD-11 has a flare at the bottom but from reading, it sounds a lot more pitch sensitive than other similar aircraft, hence why Navy guys may have been preferred.

At least, that’s totally my assumption and I’ve been AFU before and might be here as well. 

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In the few jets I’ve flown, you could do either. But only in the F-15 was it a specific units of AOA you’d fly instead of just on the green donut. The others have been airspeed or AOA. The Eagle also could calculate landing speed with something similar to the T-38 (I think it was 138+gross weight or something) but AOA units was much easier.

Do airliners give you the 1.3 Vs out of some computer and it varies each time or is it a consistent speed?

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In the few jets I’ve flown, you could do either. But only in the F-15 was it a specific units of AOA you’d fly instead of just on the green donut. The others have been airspeed or AOA. The Eagle also could calculate landing speed with something similar to the T-38 (I think it was 138+gross weight or something) but AOA units was much easier.
Do airliners give you the 1.3 Vs out of some computer and it varies each time or is it a consistent speed?

I mean, I just hit request and it sends me back numbers... God forbid I have to use the iPad and calculate it myself. Lol


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FMC calculates approach speed just line select from a list of landing flap settings, enter it into the landing settings line and your V speeds for all your flap limits and approach speed appear on your display. 

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FMC calculates approach speed just line select from a list of landing flap settings, enter it into the landing settings line and your V speeds for all your flap limits and approach speed appear on your display. 

No. That can’t be right. I’m pretty sure magic is involved somewhere. Right?


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2 hours ago, Duck said:


No. That can’t be right. I’m pretty sure magic is involved somewhere. Right?


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Black magic.  I forgot the part where you light candles (it's a Boeing so the candle auto-lights after selecting the FMC approach page) and throw some crew meal chicken bones onto the center console.  This conjures up the ghost of C.R. Smith (founder of AA, other airlines have different ghost options) and once his ghost appears and "Descent Checklist" is selected, the V speeds appear on the flight display. 

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On 10/7/2019 at 4:39 PM, Bigred said:

I guess I wasn’t too clear. I’m tracking most every military plane has some sort of AOA gage. My point is that, using the 135 as an example, I may fly an approach at 165kts and reference the AOA gage, but I’m not slaved to what it says precisely, I’m more concerned with airspeed.

Ah gotya.  In the F-16 it's exactly the opposite.  I'll calculate an approach speed and QC that it generally matches up, but I'm really only concentrating on holding a particular AOA (via a "staple" in the HUD).  

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On 10/6/2019 at 11:51 AM, Muscle2002 said:

Every fighter I have flown or evaluated used AOA, but all, with the exception of the Super Hornet and Hornet, were flown in the region of "normal command" (front side) which is more intuitive to fly, IMO.

Muscle, can you explain this statement?  I don't think I'm understanding what you're trying to say, since it is counter to everything I’ve ever seen or experienced. . 

Edited by HuggyU2

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