AOA and the Hornet

[Skysurfer]

On non-FCS aircraft like say the Tomcat you trim to on speed for a specific power setting and do slight adjustments of power to control your descent rate. Pitch for speed, power for descent rate. AOA in this case is a combination of all 3 variables (power, pitch, trim) - if said conventional plane is trimmed for "on speed" no matter the power setting, it will always stay on speed by means of oscillating up and down until it settles at said AOA. Again, power controls your climb/descent (pitch&power couple moment aside). 

 

The Hornet maintains on speed AOA via trim in landing gains (if you want to know more detail, reference the NATOPS). You trim it for on speed on downwind, set baseline power for level flight and control your descent with reasonable power modulation (never go full MIL or full IDLE). AOA, or angle of attack by definition is the angle between the chordline of your wing and the relative wind and is directly tied to how much lift your wing produces. At 1G it will correspond to the desired approach speed for the boat.

 

5 minutes ago, Gripes323 said:

 

.  I wish we had a target AOA display on HUD (low on the right side). Some lots of Super Hornets have them. It allows the pilot to set the desired AOA with the trim hat ahead of time and as the jet slows down, the bracket lines up, all the pilot has to do is maintain the glide path with the throttle.

 

If only there was a means of telling your target AOA (as well as range) somewhere.... I wonder. The legacy Hornet is flown exactly the same. 

[maxTRX]

6 minutes ago, =4c=Nikola said:

 

Yea, that sounds like a good idea on paper, but if you rush to trim for on-speed AoA you end up mistrimmed for some time. Idk, I would need to try it first to decide whether I like that feature.

Supposedly it works good... just repeating what I've heard.  Even with minor corrections, this feature would speed things up a bit.

[Swift.]

15 minutes ago, Skysurfer said:

If only there was a means of telling your target AOA (as well as range) somewhere.... I wonder. The legacy Hornet is flown exactly the same. 

So there is, but that came with MC OFP 23X. Which came in around 2011 iirc

 

MC OFP 23X is amazing btw, target AOA, DUAL altitude in the HUD (Radar and Baro up to 5000, HAT and Baro above 5000), etc ,etc

[Skysurfer]

26 minutes ago, Swiftwin9s said:

So there is, but that came with MC OFP 23X. Which came in around 2011 iirc

 

MC OFP 23X is amazing btw, target AOA, DUAL altitude in the HUD (Radar and Baro up to 5000, HAT and Baro above 5000), etc ,etc

 

That is cool and all but I was more hinting at the fact that you have an AOA bracket and indexer to trim for your desired AOA. 

[maxTRX]

20 minutes ago, Skysurfer said:

 

That is cool and all but I was more hinting at the fact that you have an AOA bracket and indexer to trim for your desired AOA. 

faster setup... it would make SHB's easier

[Stearmandriver]

7 hours ago, Pieterras said:

@Steaemandriver  @Bunny Clark

 

Use of this technique during approach on commercial jet airplanes would be contrary to the pitch commands provided by the flight director bars, and to the speed hold mode of the autothrottle, which is often used during approach. In a commercial plan you can see your AOA pretty clearly as it is roughly the difference between your Flight Path Vector and your pitch indication. 

Again... you don't care about airspeed during approach in any aircraft, you only care about AoA.  In civilian aircraft, we often use airspeed as a proxy indicator of AoA, but it's not speed that matters... it's ONLY AoA.

 

That's exactly what the flight director / HUD speed commands are telling you; they're driving you to hold the airspeed the FMC has computed will yeild the proper AoA.

 

In my fleet at work, we do have an AoA indicator in the HUD, we do train to fly an approach using it (although as an abnormal, in the event of an unreliable airspeed event), and the check airmen that truly understand AoA (many of whom are former fighter guys) are careful to point out that it's good technique to use any time.  I've had fun discussions with a couple of the others who don't understand it. 

 

There's nothing special about a fighter during landing.  It's just another jet.  The same AoA margin below critical that yeilds the proper energy state for approach in a jet that starts with an F, is also correct for one that starts with a B or A.  

Edited May 8, 2021 by Stearmandriver

[Stearmandriver]

Also, there was a bit of ridicule on the last page at the notion that throttle could affect AoA.  While I understand the point that in the Hornet in PA mode, the FCS pitches to maintain the trimmed AoA, it's fair to point out that in general, it IS true that throttle does affect AoA; there's no reason to ridicule that notion.  In any plane, throttle will affect airspeed, and airspeed changes will affect AoA.  Remember, pitch and power are always connected... changing one means you WILL be changing the other.  It's just that in the Hornet, the FCS controls the pitch for you. 

3 hours ago, Skysurfer said:

At 1G it will correspond to the desired approach speed for the boat.

Yup, and at ANY g, it will correspond to the correct airspeed for that wing loading.  That's the beauty of directly flying AoA instead of airspeed - you will always be at the correct energy state, with no concerns about load factor changes related to bank angle, gust factor etc. 

[TimRobertsen]

16 hours ago, Gripes323 said:

faster setup... it would make SHB's easier

There is a way 

 

(although, I think it might be a bug, it doesn’t seem to be a feature on real Hornets)

I don’t know if people do it this way, but I’ve never seen it mentioned anywhere.

 

I “found” it when I was trying to find a way to avoid the ballooning-effect caused by the flaps deploying.

 

It bypasses the entire process of “working down” the airspeed to on-speed-AoA 

 

With flaps in Auto, gear extended, throttle in idle and airspeed decreasing: when the velocity vector passes through the ideal AoA on the E-bracket, set flaps to half and then quickly tap nose-up-trim.

This will lock the trim to AoA the aircraft had at the moment you tapped the nose-up-trim. After the tap you simply let go of the stick and let the Hornet glide into on-speed-AoA; or, if you're in a hurry (SHB) you can keep pulling pitch until you get closer to the on-speed-AoA/stall-speed, at which point you have to add some throttle or transition to throttle-for-pitch

 

This can be done during turns, level flight, ascending, descending; and with pitch-input from the stick: in cases where you missed the mark and have to “force” the aircraft to the ideal AoA for the tap.

 

This will of course mean that the flaps are extended at a lower airspeed than your typical 250kts, unless you’re pulling G’s/are in a high AoA-state (SHB for example).

[Mover]

18 hours ago, Skysurfer said:

 

That is cool and all but I was more hinting at the fact that you have an AOA bracket and indexer to trim for your desired AOA. 

Which is not as precise as trimming to 8.1 in the HUD or using the channel address (I forget what it is because I only had to use it a few times flying the B model).  

[maxTRX]

2 hours ago, Mover said:

Which is not as precise as trimming to 8.1 in the HUD or using the channel address (I forget what it is because I only had to use it a few times flying the B model).  

,  

channel address?  I think I 'kinda' know what that means.  If you could explain, in one sentence ... or two

[Mover]

1 minute ago, Gripes323 said:

,  

channel address?  I think I 'kinda' know what that means.  If you could explain, in one sentence ... or two

 

The sentence above where I said I forgot is about as good as it gets.

 

Old school guys used it.  It was an FCS sub-menu channel address where you'd trim to a specific number.  I haven't flown the Hornet in 5 years and only did it maybe 2-3 times.  8.1 in the HUD is what everyone used (although some old school guys still did the channel thing).  

[Skysurfer]

2 hours ago, Mover said:

Which is not as precise as trimming to 8.1 in the HUD or using the channel address (I forget what it is because I only had to use it a few times flying the B model).  

 

No doubt. Simply not used to it (nor did I know about this feature until very recently) from DCS. What's the rough margin of error / leaway in terms of AOA when on yellow donut indexer?

[maxTRX]

4 hours ago, TimRobertsen said:

There is a way 

 

(although, I think it might be a bug, it doesn’t seem to be a feature on real Hornets)

I don’t know if people do it this way, but I’ve never seen it mentioned anywhere.

 

I “found” it when I was trying to find a way to avoid the ballooning-effect caused by the flaps deploying.

 

It bypasses the entire process of “working down” the airspeed to on-speed-AoA 

 

With flaps in Auto, gear extended, throttle in idle and airspeed decreasing: when the velocity vector passes through the ideal AoA on the E-bracket, set flaps to half and then quickly tap nose-up-trim.

This will lock the trim to AoA the aircraft had at the moment you tapped the nose-up-trim. After the tap you simply let go of the stick and let the Hornet glide into on-speed-AoA; or, if you're in a hurry (SHB) you can keep pulling pitch until you get closer to the on-speed-AoA/stall-speed, at which point you have to add some throttle or transition to throttle-for-pitch

 

This can be done during turns, level flight, ascending, descending; and with pitch-input from the stick: in cases where you missed the mark and have to “force” the aircraft to the ideal AoA for the tap.

 

This will of course mean that the flaps are extended at a lower airspeed than your typical 250kts, unless you’re pulling G’s/are in a high AoA-state (SHB for example).

Nah

Flying with bunch of AI Hornets, in just about every recovery cycle I get to break the deck... sometimes literally. I just yank like crazy, ease up, check a/s and alt., look back, hit the gear and flaps in one motion and then the 'work' starts.

5 minutes ago, Mover said:

 

The sentence above where I said I forgot is about as good as it gets.

 

Old school guys used it.  It was an FCS sub-menu channel address where you'd trim to a specific number.  I haven't flown the Hornet in 5 years and only did it maybe 2-3 times.  8.1 in the HUD is what everyone used (although some old school guys still did the channel thing).  

 Fair enough, thanks. I was speculating somewhere along these lines.

[Brun]

1 hour ago, Skysurfer said:

 

No doubt. Simply not used to it (nor did I know about this feature until very recently) from DCS. What's the rough margin of error / leaway in terms of AOA when on yellow donut indexer?

 

7.4 to 8.8 degrees.

[Bunny Clark]

6 hours ago, Gripes323 said:

,  

channel address?  I think I 'kinda' know what that means.  If you could explain, in one sentence ... or two

Off the top of my head from memory, so I may not be entirely correct here: there's a way, in the FCS page, to "bit interrogate" a value held in the FCS computer memory. One of these stored bits is the commanded AoA value. You go into the Bit Interrogate sub-page, enter the memory address for the specific bit, and you'll end up with a number that represents the current commanded AoA displayed on the DDI. It won't be in degrees, so Hornet pilots figured out what the value needs to be for the FCS to be set to on-speed and would adjust trim until the bit value was correct. 

 

This became common enough practice in the fleet it was added as an official function in a software update, which is where the commanded AoA value in the HUD came from. 

 

I don't believe this system is modeled at all in DCS. 

Edited May 9, 2021 by Bunny Clark

[maxTRX]

1 hour ago, Bunny Clark said:

Off the top of my head from memory, so I may not be entirely correct here: there's a way, in the FCS page, to "bit interrogate" a value held in the FCS computer memory. One of these stored bits is the commanded AoA value. You go into the Bit Interrogate sub-page, enter the memory address for the specific bit, and you'll end up with a number that represents the current commanded AoA displayed on the DDI. It won't be in degrees, so Hornet pilots figured out what the value needs to be for the FCS to be set to on-speed and would adjust trim until the bit value was correct. 

 

This became common enough practice in the fleet it was added as an official function in a software update, which is where the commanded AoA value in the HUD came from. 

 

I don't believe this system is modeled at all in DCS. 

 

 

I would imagine this was done during pre-taxi setup not during approach. Some day perhaps ED throws it in as an Easter egg or who knows... they might have a plan to model more advanced features. If they do, I hope this address is selectable by highlighting a line from the list not by typing hex numbers 

[Mover]

34 minutes ago, Gripes323 said:

 

I would imagine this was done during pre-taxi setup not during approach. Some day perhaps ED throws it in as an Easter egg or who knows... they might have a plan to model more advanced features. If they do, I hope this address is selectable by highlighting a line from the list not by typing hex numbers 

 

It was done during approach when you needed to trim on-speed.  

[maxTRX]

1 hour ago, Mover said:

 

It was done during approach when you needed to trim on-speed.  

 

Ah, I see.  I guess the process was probably not that complicated then, considering how fast things happen at this part of approach. 

[HILOK]

i agree on most of your statements, but you lost me a bit on those two 

On 5/8/2021 at 9:18 PM, Stearmandriver said:

That's exactly what the flight director / HUD speed commands are telling you; they're driving you to hold the airspeed the FMC has computed will yeild the proper AoA. 

 

In my fleet at work, we do have an AoA indicator in the HUD, we do train to fly an approach using it (although as an abnormal, in the event of an unreliable airspeed event), and the check airmen that truly understand AoA (many of whom are former fighter guys) are careful to point out that it's good technique to use any time.

...yes, but only in mode CLIMB/IDLE DESCEND as far as i know. in ALT/VNAV/APCH mode FD commands keep the aircraft on altitude/glide path, and power controls SPD...i was under the impression this thread centers around power approach.

 

...you are probably referring to the airbus BUSS. but tbh outside of that i never heard of applying AOA/PA techniques on a commercial jet. especially during manual approach, where glide path is usually kept with pitch, and SPD controlled using power, as opposed to PA: keeping SPD using pitch, controlling glide using power. i dont think both techniques mix up well, it's either or, and it depends on aircraft design/instrumentation, as far as my understanding goes.

[HILOK]

On 5/8/2021 at 5:47 PM, Pieterras said:

Spool-up times? If dcs was off in spool-up times this would be almost impossible To notice for the average flight simmer and definitely for the once that doesn’t understand AOA in the first place. As a pilot I can assure you the spool-up characteristics are quick close to how a jet engine reacts and definitely close enough not to cause any issues in DCS. If you find it an issue, then 99% the issue is you.

i very much appreciate your knowledgeable inputs in this forum. and if the hornet FM/engine model are proven to be spot on, i'll rest my case, and accept that i am the issue. could be that the problem is just the missing butt-feeling that in RL would immediately tell you how much power to apply without overcorrecting. did you have a look at the facts presented in that engine spool time thread?

i would be highly interested in your feedback about those. thanks 

[Stearmandriver]

14 minutes ago, HILOK said:

i agree on most of your statements, but you lost me a bit on those two 

...yes, but only in mode CLIMB/IDLE DESCEND as far as i know. in ALT/VNAV/APCH mode FD commands keep the aircraft on altitude/glide path, and power controls SPD...i was under the impression this thread centers around power approach.

 

...you are probably referring to the airbus BUSS. but tbh outside of that i never heard of applying AOA/PA techniques on a commercial jet. especially during manual approach, where glide path is usually kept with pitch, and SPD controlled using power, as opposed to PA: keeping SPD using pitch, controlling glide using power. i dont think both techniques mix up well, it's either or, and it depends on aircraft design/instrumentation, as far as my understanding goes.

Airbus?  Ew. 

 

No, this is on a Boeing.  There are multiple commanded speed indications on the PFD, and there are direct flight guidance cues in the HUD (ie, part of the flight director system) that provide guidance to achieving the commanded speed, no matter which flight guidance or HUD mode is selected.  So, the flight director is always providing speed commands, as well as pitch and roll commands. 

 

You are correct that transport aircraft are usually flown on approach by adjusting pitch for glideslope and power for airspeed, but of course it's not that simple.  They're inextricably linked, and a change in one will almost always require a change in the other.  New pilots are taught this method to give them a concrete way of fixing speed and glidepath deviations, but as a pilot gets more comfortable handflying the aircraft, they start to use pitch and power in a more connected manner.  For instance, when I cross the parking garage for 27 in San Diego and it's time to duck a little, I don't pitch down... I reduce power briefly.  That induces a brief settle and keeps me on speed. 

 

... which really means, keeps me on AoA.  What I was trying to say is that, even if we don't directly reference AoA in these aircraft (though we can), that's ultimately what we're trying to control, is AoA.  Speed is just used as a proxy indication of AoA.  The problem with this is, indicated speed for a given AoA varies with load factor, weight, cg, and other things.  But the proper AoA never changes... so doesn't it make more sense to just directly fly AoA if you can?  (Regardless of whether you think about controlling AoA with pitch or power. )

5 minutes ago, HILOK said:

did you have a look at the facts presented in that engine spool time thread?

i would be highly interested in your feedback about those. thanks 

Agreed.  I do really enjoy the DCS Hornet flight model - it does actually achieve that elusive ability to "feel like a jet" that is so darn hard to find in a desktop sim.  But there's no denying that the evidence presented in that thread indicate that the DCS spool times are simply wrong. 

[Pieterras]

1 hour ago, HILOK said:

i very much appreciate your knowledgeable inputs in this forum. and if the hornet FM/engine model are proven to be spot on, i'll rest my case, and accept that i am the issue. could be that the problem is just the missing butt-feeling that in RL would immediately tell you how much power to apply without overcorrecting. did you have a look at the facts presented in that engine spool time thread?

i would be highly interested in your feedback about those. thanks 

Well maybe spot on is not the the right wording. It is quite simple to be honest. Looking at the facts at first sight it seems that yes the spool up time, over the entire range of thrust settings seems a little slower then the rl. 404 however it is impossible to determine that from

- A video comparison,

- Timing equipment,

- Performance table comparison

- By just feel in DCS. 

 

The only way to test it properly is to attach the engine to a computer and then see what the actual output is, compare it to the real life output figures and adjust were necessary. And to use a throttle with the exact same mechanics and movement range.  
 

We in DCS have no option to determine this. Maybe it’s the equipment some of us use, maybe the curves ? The delay might only be in a certain area of the thrust range,  it might not be a delay but simply a lower spool time, but we have no idea wether it is one on one in the range used during the approach, if it is any particular area of the entire range of the engine. 

 

What is very easy to state is that the lack of seat of the pants, is the biggest factor when it comes to over compensation of flying the DCS hornet and I would say an added factor is that many have no aviation background and a below average understanding of the actual mechanics of engine performance and or flying mechanics. 

 

I have seen the documentaries you mentioned and I find in DCS you have to walk the throttles too. Many guys I have watched on YouTube are overcorrecting but all self induced. Maybe wrong curves, not enough friction, a wrong technique so no 3phase power corrections. And the worst of all, only a few fly with an actual gameplan of how they will fly their approach. Many fly reactive instead of proactive and yes this will automatically bring over controlling especially on the ball. 

so as I said before yes maybe the timing is slightly off, but it has no effect of how the hornet in dcs can or should be operated. What I don’t get is that we keep slagging of the hornet whilst much less performing modules can’t get enough credits whilst being far from the hornets level of detail, accuracy or ability. 

 

 

 

 

Edited May 10, 2021 by Pieterras

[HILOK]

4 hours ago, Pieterras said:

I have seen the documentaries you mentioned and I find in DCS you have to walk the throttles too. Many guys I have watched on YouTube are overcorrecting but all self induced. Maybe wrong curves, not enough friction, a wrong technique so no 3phase power corrections. And the worst of all, only a few fly with an actual gameplan of how they will fly their approach. Many fly reactive instead of proactive and yes this will automatically bring over controlling especially on the ball. 

thanks! two more questions, if you dont mind: in DCS, once you are trimmed for proper AOA, do you completely refrain from touching the pitch axis at all? and, have you tried night landings with turbulence factor set to 50 in the ME? -should equate gusts of 3kt, which is not much really. i would be interested in your judgement about how the DCS hornet FM compares to the real one in that case.

 

4 hours ago, Pieterras said:

What I don’t get is that we keep slagging of the hornet whilst much less performing modules can’t get enough credits whilst being far from the hornets level of detail, accuracy or ability

that may just be due to the fact that currently it's one of the most popular modules.

[HILOK]

@Stearmandriver thanks for the clarification. oh no, the mighty boeing!! -how could i  didn't mean to offend you 

[Pieterras]

In DCS I don't think I ever had to help the aircraft in pitch once trimmed for on-speed AOA. but this is purely in DCS. 
Turbulence factor of 50 in the ME is nothing like a 3kt gust.. Tbh a 3kt gust... probably be ignored by every pilot once heard on the ATIS, of by ATC, however the factor 50 in the ME means hard work ..