My book "Angle of Attack" is out!

PeanuckleCRJ said:
Given that even I have been flying jets since before RVSM, yes, they all had said experience with certainty, and years of it. :)



Be careful on your wording, as it is extremely important... ALT 2 is "alternate law," which is the overall FBW regime that you're in. Direct law is another overall FBW regime with protections all gone.

Aileron control in ALT 2 is directly controlled by stick input, but it is not in "direct law." The difference, while subtle, is critical. She is twitchier in the roll, but it isn't awful... the 330 is very very stable with the phase length of control input to response almost twice as long as the 320. The 320 series has a much higher roll rate and is downright touchy in the roll in alternate and direct law (I've had the real thing in both laws in flight). One characteristic to note about the 330 in the roll is its behavior in heavy turbulence- it tends to wobble around up to about 7-10 degrees of bank.
Click to expand...

I had flown the FAA A330 simulator in ALT 2 to 10 degrees past stall (not stall warning, but stall) AoA. I found it to be very easy to overcontrol with very low damping. This was a FL350 so low q factor. What altitude did you do this at?

Elaborate on how the pilot would perceive a difference between aileron control "directly controlled by stick input" (so not a rate control) and "direct law".
 
seagull said:
I had flown the FAA A330 simulator in ALT 2 to 10 degrees past stall (not stall warning, but stall) AoA. I found it to be very easy to overcontrol with very low damping. This was a FL350 so low q factor. What altitude did you do this at?

Elaborate on how the pilot would perceive a difference between aileron control "directly controlled by stick input" (so not a rate control) and "direct law".
Click to expand...

Perhaps since I was coming from the 320, I found the 330 particularly easy to control in alternate (both flavors, with ALT 1 being very docile) and direct. I've done stalls from near the ground to FL410.

The difference with direct law is that all flight controls go to direct control, all protections are lost, and manual trimming must be accomplished... thus it goes from "twitchy" in just the roll axis to "twitchy" in all. Alternate law on the 330 does not even equate to direct control of the ailerons... that only happens in ALT 2.
 
OK, we're on the same page. I am only talking about the case of ALT2, and the roll axis. If someone had not experienced it before (and it was not part of any training) it would come as quite a surprise.

I am curious, how did you come to fly them in direct law in the real airplane? FFT?
 
PeanuckleCRJ said:
Perhaps since I was coming from the 320, I found the 330 particularly easy to control in alternate (both flavors, with ALT 1 being very docile) and direct. I've done stalls from near the ground to FL410..
Click to expand...

Were the stalls in the sim or the airplane? If the sim, which sim (who owned it) did you use?
 
seagull said:
OK, we're on the same page. I am only talking about the case of ALT2, and the roll axis. If someone had not experienced it before (and it was not part of any training) it would come as quite a surprise.

I am curious, how did you come to fly them in direct law in the real airplane? FFT?
Click to expand...

At least for us, every recurrent every 9 months you put the airplane into ALT 2 and do at least 1 stall. It should not come as a surprise how she behaves in ALT2, as the "twitchiness" is highly emphasized and experienced every time you go to video game world. All the sims are touchier than the real plane.

And yes, functional check flights were when we did alternate and direct law. Via the script, we would trigger an alpha floor event in normal law, and a bit later on we would degrade the plane into alternate law to check the protections there. On the 320, to get it into direct law from alternate, all you have to do is drop the landing gear. The FBW matrix of degradation on the 330 is significantly more refined, so you have to be a lot meaner to it to get it into direct law.
 
PeanuckleCRJ said:
Truthiness! Very telling that Boeing put a virtually identical function on the 777 and beyond with identical inhibit windows, but just different enough to where they tout it as their own.
Click to expand...

I am not sure what mode you refer to? I am not aware of this, can you elaborate? Would be nice to have!

Also, the 777 really has no real low speed protection. It has an inhibit for trimming below the foot so it gets heavier, and the autothrottles only will respond in certain modes. If there is a mode that does more I'd love to learn about it.
 
PeanuckleCRJ said:
At least for us, every recurrent every 9 months you put the airplane into ALT 2 and do at least 1 stall. It should not come as a surprise how she behaves in ALT2, as the "twitchiness" is highly emphasized and experienced every time you go to video game world. All the sims are touchier than the real plane.

And yes, functional check flights were when we did alternate and direct law. Via the script, we would trigger an alpha floor event in normal law, and a bit later on we would degrade the plane into alternate law to check the protections there. On the 320, to get it into direct law from alternate, all you have to do is drop the landing gear. The FBW matrix of degradation on the 330 is significantly more refined, so you have to be a lot meaner to it to get it into direct law.
Click to expand...

Interesting on the training in degraded law. Do you know if that was always part of the training or only since the AF447 accident?
 
seagull said:
I am not sure what mode you refer to? I am not aware of this, can you elaborate? Would be nice to have!

Also, the 777 really has no real low speed protection. It has an inhibit for trimming below the foot so it gets heavier, and the autothrottles only will respond in certain modes. If there is a mode that does more I'd love to learn about it.
Click to expand...

I'm speaking of autothrottle wake up, which is analogous to alpha floor with differences in which Boeing made it their own. As far as I have read, they have the 100 RA inhibit and it just "wakes the thrust up" and adds power to try to keep you from getting too stupid. Is my understanding close?

On the bus, if you're above 100 RA, in normal law, and the autothrust is functional (doesn't have to be on), exceeding a certain AOA, AOA rate of change, and in combination with side stick inputs, the autothrust will turn on and go directly to TOGA power. To get it out of TOGA power, the conditions resulting in the A.FLOOR thrust mode have to be removed, and the auto thrust has to be turned off to remove the subsequent TOGA LK ( autothrust locked in TOGA) mode. It can get quite sporty!

seagull said:
Interesting on the training in degraded law. Do you know if that was always part of the training or only since the AF447 accident?
Click to expand...

It's been part of the training since the first delivery in 1990(ish).
 
Last edited:
PeanuckleCRJ said:
I'm speaking of autothrottle wake up, which is analogous to alpha floor with differences in which Boeing made it their own.

It's been part of the training since the first delivery in 1990(ish).
Click to expand...

Yes, I wish it was as robust as the Bus. Another feature you have is the ability to hold full aft stick to net L/Dmax, as I recall. What is it called again?

On the training, good on you guys and gals to have done that. Many operators still do not.
 
seagull said:
Yes, I wish it was as robust as the Bus. Another feature you have is the ability to hold full aft stick to net L/Dmax, as I recall. What is it called again?
Click to expand...

Now that right there is a glorious thing! It's a function of normal law... the stick at full aft will command the maximum of whichever is most limiting: 2.5 Gs, 30 degrees nose up, or max alpha.

That combined with A.FLOOR and automatic spoiler retraction when TOGA power is commanded makes for absolute maximum performance just when you need it the most.
 
PeanuckleCRJ said:
Now that right there is a glorious thing! It's a function of normal law... the stick at full aft will command the maximum of whichever is most limiting: 2.5 Gs, 30 degrees nose up, or max alpha.

That combined with A.FLOOR and automatic spoiler retraction when TOGA power is commanded makes for absolute maximum performance just when you need it the most.
Click to expand...

Yes, truly brilliant. Is there a formal name for it? I thought there was, but my memory is foggy.
 
seagull said:
Yes, truly brilliant. Is there a formal name for it? I thought there was, but my memory is foggy.
Click to expand...

It's just part of the matrix of pitch, bank, load factor, and speed/alpha protections of normal law. Airbus of course has gotten slicker and slicker as time has gone on introducing ALT 1 and ALT 2 in the 330/340 (alt 1 is really just normal lite with most of the protections remaining), and then going even further with it on the 380 and 350.
 
seagull said:
Mike,

Exactly. I would challenge even most check airman to know all the nuances of all modes of either the Bus or Boeing. The "what's it doing now" joke is a direct consequence of not understanding it, and a clue that you need to learn it more.

On the stall, it turns out the lateral motion is quite a challenge to handle. It goes into direct law and, as you wrote, lateral motion is induced by the aero effects (as Pinker outlined in his paper in the 1963, calling it a "Lanchester" oscillation) and with little damping it is easy to overshoot corrections. This significantly adds to the cognitive workload.
Click to expand...

Full stalls in the T-38 were definitely uncomfortable, with the feeling of being in a rapidly falling elevator, with a pegged VSI gauge, while still looking out front at the horizon or slightly higher, as the plane rocked side to side, with pilot roll inputs having no noticeable effect....the jet was going to do its thing in the stall. Rudder did little, as with the landing gear retracted, there's only 6 degrees travel. No nose fall-through like a straight-wing aircraft, and when holding it in the stall with aft stick, you're losing about 8000-10000 fpm. This was one of the reasons that the T-38 is known unfortunately for the number of base/90 to final-turn accidents in the USAF, as if one isn't monitoring and managing their G coming around the turn, the sink rate they can induce will rapidly onset in an insidious manner. By the time the pilot notices the rapid rise of terra firma in his peripheral vision as the plane blows through the glidepath in his forward vision as he's rolling around to runway heading, any ability to recover.....or to successfully eject for that matter......has long been passed.

In training in the F-117, understanding the aerodynamics was exceptionally important for a few reasons. Due to the permanent 68 degrees of wing sweep, low speed operations (a relative term, as being an approach Cat E aircraft, with ~170-180 on the approach speed) could get tricky. Also due to being both statically and dynamically unstable, with the fly-by-wire "managing" the instability to allow the plane to fly, the pilot had to know solidly what the airplane flight control systems were doing and why they were doing it. The big point here is that there was no shortcutting that knowledge and training, it was paramount. Why that kind of training or knowledge isn't trained to that level or more with larger and more complex/ more systems transport-category aircraft, is surprising. Literally, the crew and their pax lives could depend on that knowledge base being there. Equally as important as the airmanship and basic piloting skills.
 
Last edited:
PeanuckleCRJ said:
It's just part of the matrix of pitch, bank, load factor, and speed/alpha protections of normal law. Airbus of course has gotten slicker and slicker as time has gone on introducing ALT 1 and ALT 2 in the 330/340 (alt 1 is really just normal lite with most of the protections remaining), and then going even further with it on the 380 and 350.
Click to expand...

Thanks for all that. There are many, many aspects of the Airbus that I wish we had on the Boeing, not least of which are the sidesticks, but aspects such as the full stick aft are really good. The envelope protections are, for the most part, good also. The Boeing is a bit better in issues such as the frozen AoA vane leading to a dive scenario. Both need work on better alerting and FMAs.
 
MikeD said:
Full stalls in the T-38 were definitely uncomfortable, with the feeling of being in a rapidly falling elevator, with a pegged VSI gauge, while still looking out front at the horizon or slightly higher, as the plane rocked side to side, with pilot inputs making having no noticeable effect....the jet was going to do its thing in the stall. Rudder did little, as with the landing gear retracted, there's only 6 degrees travel. No nose fall-through like a straight-wing aircraft, and when holding it in the stall with aft stick, you're losing about 8000-10000 fpm. This was one of the reasons that the T-38 is known unfortunately for the number of base/90 to final-turn accidents in the USAF, as if one isn't monitoring and managing their G coming around the turn, the sink rate they can induce will rapidly onset in an insidious manner. By the time the pilot notices the rapid rise of terra firma in his peripheral vision as the plane blows through the glidepath in his forward vision as he's rolling around to runway heading, any ability to recover.....or to successfully eject for that matter......has long been passed.

In training in the F-117, understanding the aerodynamics was exceptionally important for a few reasons. Due to the permanent 68 degrees of wing sweep, low speed operations (a relative term, as being an approach Cat E aircraft, with ~170-180 on the approach speed) could get tricky. Also due to being both statically and dynamically unstable, with the fly-by-wire "managing" the instability to allow the plane to fly, the pilot had to know solidly what the airplane flight control systems were doing and why they were doing it. The big point here is that there was no shortcutting that knowledge and training, it was paramount. Why that kind of training or knowledge isn't trained to that level or more with larger and more complex/ more systems transport-category aircraft, is surprising. Literally, the crew and their pax lives could depend on that knowledge base being there. Equally as important as the airmanship and basic piloting skills.
Click to expand...

Fantastic post, Mike. You also got to feel that free fall effect, which I do believe really messed up the AF447 crew (among other factors). In my surveys I have found most pilots surprisingly lacking any foundation. Peanuckle here has been quite refreshing. If more pilots had his knowledge base we'd have a lot safer industry.
 
@Mike, was the seat in the -38 different than the one in the F-5? Because I know my bros in that hog have a safe window that begins at or above 10k ft
 
seagull said:
Thanks for all that. There are many, many aspects of the Airbus that I wish we had on the Boeing, not least of which are the sidesticks, but aspects such as the full stick aft are really good. The envelope protections are, for the most part, good also. The Boeing is a bit better in issues such as the frozen AoA vane leading to a dive scenario. Both need work on better alerting and FMAs.
Click to expand...

Agreed! I do wish that the sidesticks were interconnected... I've thought about going to the 777, but my desire to have a yoke in front of me again is extremely low. There are human factors issues with being slaves to the autothrust parked in the CL detent as well... I understand why they did it as they want you to be looking at the FMA and the engine indications instead of switch position, but there is a tendency, particularly with noobs, to just go "ok its in the CL detent, I'm ok." Nope nope nope!

I'd love to see some real out of the box and forward thinking on better FMAs in particular.

That AoA vane issue is a reason why we have the now memory item to degrade the plane into alternate law. The final straw was quite the interesting occurrence... it wasn't a dive at all. The vanes locked at a lower altitude, and as they climbed up the A-prot strip on the speed tape slowly climbed up and eventually overtook their airspeed (alpha tolerance window decreases as mach increases). The airplane doesn't react immediately to touching A-prot... it's lazy and will go about 5 knots in every time before it goes "ok, fine... I'll do something about this" and kicks off the autopilot and inserts a nose down moment. All that happened was they just drifted down for a short period, got the AP on, said "well that was weird... stupid French airplane," and wrote it up when they landed.

Check out the ANZ accident on their acceptance flight of a used LH 320 for the exact opposite happening with locked alpha vanes in a good position. It let them deep stall the plane thinking it was in a good alpha... unfortunately they were cutting corners and did the stall at low altitude. That resulted in the death of all on board. It's a bit ironic that the relatively benign event where they just wafted down barely 1000 feet was the last straw instead of that one.
 
Peanuckle, agreed on all you wrote, I was familiar with the low and high speed AoA for stall issue. Although the algorithm for adjusting AoA for mach effect is common on the newer airplanes, most don't have the alpha protection feature to create that scenario. Actually, I am not sure how many false stall warnings the other types get either, so there is another aspect going on. Have you looked into this at all? I am well aware of how it happened on the Airbus, but would not that same scenario lead to at least errant stick shaker in other types? Or is there something else going on here?
 
You must log in or register to reply here.
Back
Top