Looping in a Level-D

[B767300]

https://www.youtube.com/watch?v=6EgeXCvhKTM

There's so much happening, I can understand the fuel pump messages but look at the PFD.

ATT flags, TCAS caution messages, It's like the IRS can't process certain angles.

[Jeroen Hoppenbrouwers]

Wild guess: the IRS technically probably could do it (with solid-state/laser/... not mechanical gyros and cardano rings), but it certainly got out of certification limits and thus legally may have declared itself unreliable.

Also always a guess what the sim does. I think there were cases when somebody tried this and the thing simply locked up, panicked, and froze "upside down".

[B767300]

Could it be a sim specific thing? Because looking at the vid again, the IRU's started malfunctioning in the dive, near the nadir.

[Hardy Heinlin]

The ROLL flag appears when there is a disagreement between the captain's and first officer's attitude indications, usually between the attitude of IRU L and R. The error threshold is low. I guess this is easily exceeded when the pitch approaches 90° at that high pitch rate and is probably related to certain sine/cosine functions which are, as we know, not linear but extreme sensitive near 90°. Finally, at 90°, the track computation (see ND) gives up as well because at that angle there is simply no track anymore, not even a zero track, for the same reason there's no longitudinal heading at the northpole. There's no longitude at the 90° latitude of a sphere. Just singularity.

[B767300]

The ROLL flag appears when there is a disagreement between the captain's and first officer's attitude indications, usually between the attitude of IRU L and R. The error threshold is low. I guess this is easily exceeded when the pitch approaches 90° at that high pitch rate and is probably related to certain sine/cosine functions which are, as we know, not linear but extreme sensitive near 90°. Finally, at 90°, the track computation (see ND) gives up as well because at that angle there is simply no track anymore, not even a zero track, for the same reason there's no longitudinal heading at the northpole. There's no longitude at the 90° latitude of a sphere. Just singularity.

that makes sense, does PSX model this?

[Hardy Heinlin]

Model what? You quoted my entire comment :-)

[B767300]

Model what? You quoted my entire comment :-)

😅excuse me, I meant the math behind the IRU resulting in ATT and ROLL flags at extreme nose angles. And also just in general the fuel thing, I tried it in PSX but all I got were altitude and speed related cautions/warnings.

[Jeroen Hoppenbrouwers]

Also keep in mind this is a SIMULATOR. Nearly everything in such a sim is simulated by software; there are only very few real avionics LRUs (and their software) involved, usually because it is very important to be 100% identical to the real thing for safety and too expensive to re-certify for safety training. Typical examples: TCAS, (E)GPWS.

Doing a looping in a real 747 probably is truly too dangerous to try. A barrel roll and a looping are quite different things.

[B767300]

Also keep in mind this is a SIMULATOR. Nearly everything in such a sim is simulated by software; there are only very few real avionics LRUs (and their software) involved, usually because it is very important to be 100% identical to the real thing for safety and too expensive to re-certify for safety training. Typical examples: TCAS, (E)GPWS.

Doing a looping in a real 747 probably is truly too dangerous to try. A barrel roll and a looping are quite different things.

that's true, I can see the fuel thing happening irl though, it's level D after all. But yeah the IRS programming may simply not be as realistic, since you'd never have to dogfight in a 74 XD... right?

[Hardy Heinlin]

How the real 744 pumps behave in a loop probably depends on the applied g-force and tank quantities. I can only speculate. The failures in the video – IRU and fuel – will not automatically occur in PSX in a loop. But you can program them on the Instructor to occur at a specific condition, e.g. at a specific airspeed, altitude, heading, distance, time etc. which will greatly vary in a loop. E.g. "when airspeed is 110 knots" etc.

[Hardy Heinlin]

Here's a 737 sim, looping and rolling:

https://youtu.be/KCVXH7VcZt0

It has an EFIS attitude. There, the ROLL flag seems to appear and disappear when passing a 180° bank angle, no matter what direction.

[B767300]

It'd be great to see these two effects in PSX, but on the other hand I doubt it's worth your time😅 you'd need to calculate sim gforces, decide when fuel sloshes and how, know the exact limits of the IRU......

[Bluestar]

I have almost 20 hours in one of the new B737-Max 8, Level-d sims.  It will do an aileron roll, but will not do a
split-S.

[B767300]

I have almost 20 hours in one of the new B737-Max 8, Level-d sims.  It will do an aileron roll, but will not do a
split-S.

lol. you flew in the mil right, fighters?

[Bluestar]

lol. you flew in the mil right, fighters?

I was a military pilot with over 1500 hours in Vietnam.  My bride of 55 years refers to me as the resident psycho-vet. ROFL

[B767300]

I was a military pilot with over 1500 hours in Vietnam.  My bride of 55 years refers to me as the resident psycho-vet. ROFL

XD. 1500 hrs in nam, so Im guessing USAF/N/MC? what type?

[ASCTU744]

It'd be great to see these two effects in PSX, but on the other hand I doubt it's worth your time😅 you'd need to calculate sim gforces, decide when fuel sloshes and how, know the exact limits of the IRU......

It won't be easy, but I'm sure PSX already has a g-reading, i.e. around a certain g at an axis facing away from the fuel pump ports, the pumps run dry.

Here's a 737 sim, looping and rolling:

https://youtu.be/KCVXH7VcZt0

It has an EFIS attitude. There, the ROLL flag seems to appear and disappear when passing a 180° bank angle, no matter what direction.

The ROLL flag appears when there is a disagreement between the captain's and first officer's attitude indications, usually between the attitude of IRU L and R. The error threshold is low. I guess this is easily exceeded when the pitch approaches 90° at that high pitch rate and is probably related to certain sine/cosine functions which are, as we know, not linear but extreme sensitive near 90°. Finally, at 90°, the track computation (see ND) gives up as well because at that angle there is simply no track anymore, not even a zero track, for the same reason there's no longitudinal heading at the northpole. There's no longitude at the 90° latitude of a sphere. Just singularity.

And for these maybe a random malfunction around the zenith and nadir (my irl name XD) or the 180 deg mark.

So just rough estimations in general, so the sim atleast has those features. Especially the fuel one, ACA143 had an AME onboard the pilots happened to know, he told them to pitch the nose up to fix the low press pump lights. Not significant but still

[jawomba]

Inspired by Tex Johnston's Barrel role with the Dash-80, the AAs tutorial videos with Cpt. Warren VanderBurgh about Unusual Aircraft Attitude revoveries, etc. ... and last but not least a bit out of curiosity how PSX behaves I did the following manouvers with PSX a while ago:

PSX manouvers - 360 role <- Edit, because as Hardy said, this is not a barrel role

How Boeing And A 1G Barrel Roll Defeated The DC-8. The $16 Million Gamble That Changed Aviation - @The Legendary Barrel Role
Btw. it's worth to see the whole filme 

PSX manouvers - inverted looping <- Edit.

Edit: Would be interesting to have a G and alpha indication as info tags 

Best regards,
Jan

[jawomba]

... also an interesting webpage where You can find some articles from Boeing's Edge Aero Magazin (Site is dedicated primary to 767 but the articles are more system related than sepcific for a single type):
skydiveing.co.uk

Aero 03 - Aerodynamic Principles of Large-Airplane Upsets
Aero 12 - Operational use of Angle of Attack

Jan

[Hardy Heinlin]

I think your 360 roll in your PSX video is not a barrel roll. In the video you push the stick forward when the brown side is up in order to maintain the altitude. In that phase the coffee won't stay in the cup. In a barrel roll you maintain a positive g-force through the entire 360 and the coffee will stay in the cup. It's like driving a car inside a huge barrell along the barrel and up the barrel wall, and the car will not fall down due to the centrifugal force.


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