Go Back  PPRuNe Forums > Flight Deck Forums > Tech Log
Reload this Page >

A321 A320 A319 lower one wing while flying straight?

Tech Log The very best in practical technical discussion on the web

A321 A320 A319 lower one wing while flying straight?

Old 23rd May 2021, 22:53
  #21 (permalink)  
 
Join Date: Feb 2001
Location: The Winchester
Posts: 6,079
Question for the OP - Is this the June 10th annular eclipse and (looking at your address) are you planning on this flight taking place over North America - where the eclipse is visible at sunrise?

If that's the case if side slipping/lowering the into sun wing is there a possibility you can ask the operator of the flight if it's possible to displace the planned track further to the north east than the one you have planned at the moment in order to get the extra solar elevation you need?
wiggy is offline  
Old 23rd May 2021, 23:21
  #22 (permalink)  
 
Join Date: Jan 2008
Location: Denver
Posts: 1,075
I see a significant aerodynamic problem not yet mentioned specifically (but KingAir1978 nudges up close against it.)

DRAG in a slip (where the relative wind is hitting the side-area of the fuselage, not just on the nose).

And thus rapidly-decaying airspeed, if one is also trying to hold altitude. Especially so close to the operational limits of the aircraft (A321 ceiling - 39800 feet).

Slips are a really good way of killing off airspeed (and/or altitude) - see, e.g., the final approach of the Gimli Glider.

Might be on the order of losing 15 kts IAS per minute, even at full thrust. Maybe more, if there is pitch added to hold altitude as the airspeed decays. And depending on all-up weight.

Just how long is this slip ("observation window") expected to last?

"Punctuated slipping" might be a solution - slipping for 15 seconds - return to coordinated flight for 60 seconds to regain speed - slip another 15 seconds (rinse and repeat).

Assuming any other problems can be addressed.
pattern_is_full is offline  
Old 24th May 2021, 06:15
  #23 (permalink)  
 
Join Date: May 2004
Location: Ziltoidia... indeed'd.
Posts: 356
atakacs

I used to fly BAE146 and it was not RVSM ceritified, so highest was FL280. And anyway, it really struggled to reach it,even not fully loaded. 300ft/min rate aboveFL250...
iggy is offline  
Old 24th May 2021, 07:00
  #24 (permalink)  
 
Join Date: Oct 2004
Location: australia
Posts: 185
Transport category aircraft, it is certificated for full rudder sideslips at speeds up to Vmo/Mmo. Either pilot rudder force limited or maximum rudder angle that the flight control system will reach.
I doubt that this aircraft would be thrust limited at the proposed altitude with the small sideslip angle required. If so, get a block of altitude and lose a bit of height during the observation - wouldn't be much.
Will need to select airspace which gives some operational flexibility
So, the proposal is within the certification envelope of the aircraft, the flight control system allows for flight with sideslip, may require flying without autopilot, should have the performance but may need to drift down a bit.
Use airspace that allows operational flexibility.
Most important, talk to the Ops manager/ chief pilot about the project.

Last edited by zzuf; 24th May 2021 at 07:18.
zzuf is offline  
Old 24th May 2021, 07:37
  #25 (permalink)  
 
Join Date: Oct 2009
Location: Australia the Awesome
Posts: 302
You might hear "STOP RUDDER INPUT" if you push too hard.
Roj approved is online now  
Old 24th May 2021, 08:16
  #26 (permalink)  
 
Join Date: Apr 2015
Location: Netherlands
Posts: 152
If the approved flight manual has no procedure for this manoeuvre, and if you perform it anyway, I believe you then act illegally and may be susceptible to judicial action. Better wait for an eclipse higher up above the horizon.
washoutt is online now  
Old 24th May 2021, 09:05
  #27 (permalink)  
 
Join Date: Jan 2019
Location: Northern Ireland
Posts: 62
What you need, my friend, is a Tupolev Tu-154; no winglets, wings well set-back on the fuselage, and anhedral to boot.

Good luck with that.
DuncanDoenitz is offline  
Old 24th May 2021, 09:29
  #28 (permalink)  
 
Join Date: Oct 2004
Location: australia
Posts: 185
washoutt

Don't understand this comment. What manoeuvre should the OP look for in the AFM? Steady heading sideslip? Won't be there. But for example, the steady heading sideslip component of a maximum crosswind takeoff or landing would be far more demanding than what the OP is proposing. Perhaps a complete engine failure at maximum altitude and maximum continuous power? That will result in a far more demanding situation than that proposed but it is a manoeuvre for which the aircraft is certificated. There is no procedure in any AFM concerning, say, using full control deflection - if it is required, the pilot does it - staying within the aircraft certification limits. Probably the most important in this case would be Va restrictions but it could be something like a buffet boundary, which won't be a AFM approved procedure.
zzuf is offline  
Old 24th May 2021, 10:11
  #29 (permalink)  

Only half a speed-brake
 
Join Date: Apr 2003
Location: Commuting home
Age: 43
Posts: 3,288
zzuf, like your inputs and I am ready to believe what you say about the certification.

EO at max alt and max L/D speed yields about 3 degrees of bank. As a matter of fact, no more than 5 is allowed by those certification standards. The original poster may have been asking for 10. In that perspective, even full rudder may not have enough authority to achieve what's asked.
FlightDetent is offline  
Old 24th May 2021, 11:38
  #30 (permalink)  
 
Join Date: Oct 2004
Location: australia
Posts: 185
Flight Detent, don't get carried away with engine out - it is not required in this case, just use a bit of rudder to induce sideslip and set a bank angle for zero yaw rate.Take just a minute or two to sort out what sideslip angle v's bank angle the particular aircraft type gives you. This is a standard flight test method when assessing lateral/directional stability and control.
Don't forget the Vmcg and Vmca are really just performance speeds to get you safely, considering particular handling characteristics, from brakes release to a V2 climb having had a critical engine failure at Vef. The limits are arbitrary - a higher or lower rudder force could be prescribed or different bank angle limits. It is a grave mistake to think that Vmca, for example, can be applied safely in flight conditions other than those specified in the airworthiness standards. Depending on the aircraft it may be possible to safely use, say, 10 degrees of bank towards the live engine and fly at a speed lower than scheduled Vmca - of course, this speed is not Vmca as the bank angle is not compliant. Scheduled Vmca has no meaning in normal engine out handling - power setting is probably wrong, bank angle probably wrong, rudder force applied probably wrong, sideslip angles probably not what was experienced during Vmca testing
Also don't forget that a manufacture may use Vmca determined at 5 degrees of bank (lowest compliant Vmca} but use around 3 degrees of bank for the engine out climb performance (zero sideslip minimum drag).
zzuf is offline  
Old 24th May 2021, 12:10
  #31 (permalink)  

Only half a speed-brake
 
Join Date: Apr 2003
Location: Commuting home
Age: 43
Posts: 3,288
Lost in translation, not sure what the Vmca connection is. My reaction was to your
complete engine failure at maximum altitude and maximum continuous power? That will result in a far more demanding situation
Which I find to be the other way around. By his own description, the OPs required manoeuvre is about 3x more aerodynamically displaced than an EO situation at max alt & MCT.

I still take your word for it that as part of the certifying flight tests, full rudder sideslips had been tested all the way up there. Not sure what the limiter provides at M 0,8. Thank you for confirming my 3-degree hunch.

Last edited by FlightDetent; 24th May 2021 at 18:01.
FlightDetent is offline  
Old 24th May 2021, 14:13
  #32 (permalink)  
 
Join Date: Feb 2001
Location: The Winchester
Posts: 6,079
washoutt

If the OP is catering for a specific observing group embarking at a particular airport he/she may have a very long wait for a repeat performance.

As I mentioned in post #21 one possible way of increasing the sun's elevation for this eclipse may be to shift the planned ground track - depending on where in the world this is being planned it might not need to be much of a shift, but doing that may bring in other complications (e.g. change timings, which can lead to other subtle and sometimes not so subtle changes) .. It'll be interesting to see if the OP thinks shifting the track is an option or not.
wiggy is offline  
Old 24th May 2021, 14:35
  #33 (permalink)  
 
Join Date: Feb 2019
Location: UK
Posts: 10
Surely you could just sell 5 less tickets for 24-28. Or as someone else said, move around. What do you do if you are on the other side?
muppetdodger is offline  
Old 25th May 2021, 00:03
  #34 (permalink)  
 
Join Date: Feb 2000
Location: 500 miles from Chaikhosi, Yogistan
Posts: 3,894
Muppet - when I did one of these, they sold the "window" so no moving about and they pulled the seats out on the viewing side.

@JRBT - a minute of internet sleuthing and a mail search on my computer reveals our paths crossed in Tahiti 11 years ago....

My considered opinion is that for this one flying one wing low is not advisable / practical nor feasible. Whilst I have not looked at Fred's predictions for this one, but I assume you are FL390 to get the sun's disk as high as possible. This altitude is fast approaching the limit of the flight envelops for the type (although likely you will be lightish). You don't want to be doing anything that upsets the ability of the aircraft to fly (like create more drag by flying slightly sideways). Furthermore, you can't just switch the Autopilot off and fly one wing low without ATC RVSM issues.

The best approach is to ask the charter company to contact Airbus directly via their Technical Pilot through the Airbus Tech Request channel. Airbus flight test pilots and engineers will review and advise. You don't want your charter company trying anything odd up there with you and your pax on. 2 weeks should be enough time.

Final thought - if you are going to not sell the shadowed windows, you will need the crew to fly the aircraft in heading, not track. A crosswind on a fixed track will alter the heading of the aircraft and in turn change the wingtip shadow location on the fuselage.

Good luck antumbra chasing!

Last edited by compressor stall; 25th May 2021 at 09:45.
compressor stall is online now  
Old 25th May 2021, 09:59
  #35 (permalink)  
 
Join Date: Apr 2015
Location: Netherlands
Posts: 152
Thanks for all your interesting observations. If a non-normal flight condition arises, then good airmanship dictates that all necessary actions be taken to ensure a safe flight and landing. If a 10 degree bank is considered a normal flight by the manufacturer and certificated by the aviation authority, then it's ok. If not, then not. Of course, you can always ask the manufacturer if a certain flight attitude e.g.condition is within limits and approved.
washoutt is online now  
Old 25th May 2021, 11:14
  #36 (permalink)  
 
Join Date: Dec 2013
Location: US
Age: 63
Posts: 436
Airmann

At 39,000 feet I think this would produce a very bad result.
Sailvi767 is offline  
Old 3rd Jun 2021, 19:40
  #37 (permalink)  

Only half a speed-brake
 
Join Date: Apr 2003
Location: Commuting home
Age: 43
Posts: 3,288

10 characters.

FlightDetent is offline  
Old 4th Jun 2021, 02:30
  #38 (permalink)  
 
Join Date: Oct 2007
Location: Here
Posts: 817
At the latitude of New York (which someone mentioned) one degree at a constant latitude is about 55 statute miles.

So you could achieve the 5 degree elevation change by moving your observation point approx 275 miles to the East or West.
jimjim1 is offline  

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell My Personal Information -

Copyright 2021 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.