Debunked: The Role of Aeroelastic Flutter in the Events of 9/11

To be fair....a "VG-diagram" is a graphical curve of speed over g-loads. However, as implied by "P4T", the specifics are in error.

Irrelevant to Transport category commercial airliners, as compared to small airplanes, in terms of the way the airframes are designed, and meant to last, for the cycles and lifetime OF the airframe.
 
,,,the specifics are in error.


NOT the parameters, the Speed/G-load graphing is simple physics. It is a graph that is not in dispute.

It is the implication OF a VG-Diagram that is mis-applied, by the "Pilotsfor9/11truth" webmaster.

This has been explained countless times, and in countless forae...or is it 'forums'??

Either way, the 'woo' has been debunked.
 
The use of the VG diagram seems rather unnecessary anyway, as there are really only three numbers being considered - the positive and negative G loading, and the V[sub]d[/sub] speed. The curves on the left just indicate stall speed and are basically irrelevant.

The claim really just boils down to "plane goes faster than Vd, plane falls apart due to flutter". This has been shown to be false. Displaying this on a complex diagram is unnecessary.

@SpaceCowboy, you have hinted that you think the explanation in the OP is wrong, and yet you refuse to explain why. Until you post an actual explanation, with numbers, I will no longer approve your posts.
 
So, what is the 'alternate' explanation proposed by the people who say the plane(s) couldn't have done what the "official story" says they did? Is this part of a "no-plane" theory or what?
 
So, what is the 'alternate' explanation proposed by the people who say the plane(s) couldn't have done what the "official story" says they did? Is this part of a "no-plane" theory or what?

More some kind of "fake plane", but it depends who you ask.

Let's try to keep the thread on flutter though.
 
@SpaceCowboy, you have hinted that you think the explanation in the OP is wrong, and yet you refuse to explain why. Until you post an actual explanation, with numbers, I will no longer approve your posts.
Incidentally, that is quite similar to the rules used on the BAUT forums. If questions go unanswered, concerning the subject of an OP, or hypotheses not explained, the thread is locked. Continually doing this, a poster may be permananty banned
 
..all flight time in steady cruise is at constant mach and altitude.


NOT "exactly"....but I understand what you were trying to say here.

For clarity: When we cruise at altitude, we may use different Mach numbers. Varies by airplane (B757/767 or B777, etc) and also fuel conservation parameters, and winds (headwinds versus tailwinds) and/or ATC requirements for in-trail separation....complicated, in summary.

ETA: A "judgement" call made by every Captain (or PIC). Many reasons might affect these decisions, and options, for every flight segment...even WITHIN a segment, when conditions change. (Or, ATC requests).
 
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Incidentally, that is quite similar to the rules used on the BAUT forums. If questions go unanswered, concerning the subject of an OP, or hypotheses not explained, the thread is locked. Continually doing this, a poster may be permananty banned
To be clear on how a layman such as myself sees it. SpaceC has made a claim. It has been countered by quoting regulations. SpaceC recountered with a quote from a lesser source, and pressed again countered with some point about the inclusion of the phrase "at constant Mach and altitude". However having been asked to clarify what his objection actually is, will not, or cannot explain what he feels this phrase does to bolster the claim of PfT that the wings of flight 175 should have snapped off (as illustrated in PfT animation) or any other related claim made in the discussion of this event.

That last point is , as I see it, why SpaceC is getting his posts moved to a separate thread, in Rambles. https://www.metabunk.org/threads/spacecowboy-rob-balsamos-9-11-ad-hom-and-off-topic-posts.3399/
 
Once again the salient regulation is as follows ( bolds mine)
Aeroelastic stability envelopes. The airplane must be designed to be free from aeroelastic instability for all configurations and design conditions within the aeroelastic stability envelopes as follows:
(1) For normal conditions without failures, malfunctions, or adverse conditions, all combinations of altitudes and speeds encompassed by the VD/MD versus altitude envelope enlarged at all points by an increase of 15 percent in equivalent airspeed at both constant Mach number and constant altitude. In addition, a proper margin of stability must exist at all speeds up to VD/MD and, there must be no large and rapid reduction in stability as VD/MD is approached.

With 15% being the more modern application than would have been in effect when 767s were built.

It seems that SpaceC is objecting that this is to apply for the condition that the aircraft be in level flight and maintaining a constant Mach number, and that the descent of flight 175 and the manouvering of flight 175 negates the effect of the 20% margin contained in the regulations.

I say that "it seems" to be his objection because he has not actually stated it. Instead he has simply repeated the phrase "constant Mach number and constant altitude" and cast ad homs attacks on those who do not simply succumb to his assertion that this disproves Mick, TWC, WW, and KB.
 
It seems that SpaceC is objecting that this is to apply for the condition that the aircraft be in level flight and maintaining a constant Mach number, and that the descent of flight 175 and the manouvering of flight 175 negates the effect of the 20% margin contained in the regulations.

I think it is not really a sticking point (to those of us who understand the Regs, and more importantly have actually flown a B767), and instead are mere semantics.

As 'SpaceC' most certainly knows, the turns seen made by UAL175 were not excessively steep bank angles, so any G-loads associated with a banked turn would have been minimal. (I have pointed this out, ad nauseum before, some years ago). Even a 30° angle of bank results in a G-load of only 1.2 Gs.

A simple online calculator: http://www.csgnetwork.com/aircraftturninfocalc.html
(Note that for this discussion, only bank angle and G-load are relevant, not airspeed...that relates to calculating the increase in stall speed ("Accelerated stall") as a function of an increase in bank angle.

Certainly it was observed that UAL175 increased its angle of left bank just seconds before impact, and when it was likely only at that point it had achieved the maximum recorded speeds. Certainly the airframe components were undergoing extreme stresses. But, it is a very robust design (the B767), and the wings won't just "snap off" as hilariously animated in the P4T video!!
 
In the animation the wing snaps off far enough from the tower to crash before even getting to the tower, iirc.
Yes, max speed and max g-load was reached some time in the period of the last ten seconds before impact. The aircraft only had to hold at least mostly intact, for ten seconds. It may well have had permanently warped components, it may well have started to experience destructive flutter on some surfaces, but as long as it held together for TEN seconds none of that mattered as the consequences of being torn apart by impact with a structure far outweighed any legal consequences for a pilot's mishandling the aircraft so dangerously.
 
In the animation the wing snaps off far enough from the tower to crash before even getting to the tower, iirc.
Yes, max speed and max g-load was reached some time in the period of the last ten seconds before impact. The aircraft only had to hold at least mostly intact, for ten seconds.

Yes, and in my post #57 above, I neglected to add that not always will a constant angle of bank result in the calculated G-loads. The online calculations are specific to a level, constant-altitude turn. A descending turn combined with an angle of bank can (briefly) result in lesser G-loads...conversely, initiate a climb while in a turn results in higher loads (not seen, since with UAL175 it was descending during final phase of the attack).

I should take pains to mention both examples refer specifically to pitch attitude changes, in a bank. Just as lowering the nose in straight and level flight will result in a (brief) lessening of G (even to achieve "zero-G", as we see with any of NASA's "Vomit Comet" airplanes used for astronaut training (and used by Ron Howard when shooting his film "Apollo 13" for specific scenes in the movie).

 
I thought the D in vd is "dive". not that I understand anyones diagrams, but how do you figure dive speed from level flight speeds? or can you dive and still be 'level'?
 
I thought the D in vd is "dive". not that I understand anyones diagrams, but how do you figure dive speed from level flight speeds? or can you dive and still be 'level'?

You are correct, the 'd' refers to "dive". Hence the confusion on the part of the video made and posted by the 'P4T' founder. (And all of the rest).

So, in a "dive", but strict definition, the airspeed and Mach number will not remain "constant".

Have I posted this video? (Can't recall). The flutter test for the A380 Super Jumbo. And yes, due to the physics, one can only get "so much" out of any airplane, at a specific altitude (in level flight)....however, to "push past" then gravity is included, for the dive testing and to achieve those speeds....speeds that cannot be achieved without the assistance of gravity (downward, of course!):



The above video is slightly hyperbolic (for dramatic purposes, as part of the documentary).
 
so if a commercial plane goes over mach1 does it look like this?
tumblr_lfdnc6wmQH1qz82gvo1_500.jpg
 
so if a commercial plane goes over mach1 does it look like this?
View attachment 6708

Well, more like this actual (but not very good) photo of TWA 841, post incident:

http://emiliocorsetti.com/wp-content/uploads/2013/07/Missing-slat-picture0001.jpg

External Quote:
During the course of the dive, the plane rolled through 360 degrees twice, and crossed the Mach limit for the 727 airframe. Control was regained at about 5,000 feet (1,524 m) after the first officer, with the captain in agreement, extended the landing gear in an attempt to slow the aircraft...
SOURCE

AND:


NOTE: Having watched the above video, and it is really a retrospect (as introduced in the opening segment) of some controversy that CBS News encountered by "mixing" factual and dramatic re-creation...something we certainly can observe today, hence the occasional "De-Bunking" need!), the fact that the original flight deck crew were added to the re-creation makes me chuckle, a bit, in hindsight. Near this video's 9:45 point, I think the Second Officer is lying, in order to support the other crew's story. In fact, the S/O had left the cockpit, and in his absence "Hoot" Gibson (the Captain) thought to try something unapproved...extending some Trailing Edge flaps, to alter the camber of the wing. But, on the B727, even "Flaps 1" causes the Leading Edge devices to extend. Hence, the decision to pull the Circuit Breaker for the LE flaps.

On the B727 there are six panels, part of the LE devices, called "Leading Edge Flaps", as compared to the L/E Slats. These six panels are inboard at the root, 3 each wing:

c7f8e6d9411fcb4779ee3ad590b60d85.jpg


Better angle of view:
0a469d6056a510b65b5a86396b4c07ca._.jpg





Pulling the C/B meant that the hydraulic valves (electrically powered) would not activate, and thus not shunt hydraulic pressure to the LE Flaps control actuators.

Later, the S/O returned, and was not briefed on the previous actions, so he saw the C/B out, and just pushed it in...and then chaos ensued.

Certainly, the Captain and First Officer had a vested career interest in supporting their narrative version. Still, that aside, the facts of the excessive airspeed and G-loads endured by that airplane are not in dispute, regardless.
 
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Flight 841 reached a max mach of 0.96M and experienced max of 8 g load, and suffered severe damage yet was returned to controlled flight and landed.
According to the NTSB report as reported by the FDR. Mysteriously the bulk erase feature of the CVR had been activated and the only recording was of the conversations in the cockpit some time after the plane landed.
Hmmmm....

What is the Md of a 727?
Or the Vd? This aircraft descended through 34000 feet in 33 seconds. Its average velocity downwards is in the range of 700 mph.
 
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Mysteriously the bulk erase feature of the CVR had been activated and the only recording was of the conversations in the cockpit some time after the plane landed.

Yup!!

Basic tenet for an airline pilot (crew) with something to hide. IF you, as a crew, felt that your performance was correct and above-board, then you might think of pulling the CVR C/B in order to preserve the recording, and vindicate any of your actions!!

(Keeping in mind that back then it was a 30-minute, at most, continuous loop magnetic tape).

I had heard, back in the day, of some "old-school" pilots who so paranoid about the CVR, they would bulk-erase after every leg, just in case it was "used against them" for even any minor infraction. Of course, I believe the CA of this flight used that as an "excuse"...claiming it was HIS "habit". :rolleyes:
 
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"P4T",

From a ETPS graduate who is qualified to certify aircraft under FAR part 25, (Transport category aircraft).

There is no problem with the aircraft being above Vd. Vd is designed so that the airframe is safe and has an acceptable service life within normal parameters. If you don't care about the longevity of the aircraft, it's quite possible to take it well above Vd but you might need some potential energy (altitude) to get there. The aircraft won't break up just because you've exceeded Vd; as you've seen there are margins and also atmospheric gusts and loads to consider. In smooth air at 1 g who knows what's possible!

The A380 was taken up to 0.96M during tests. The G650 has a limit Mach of 0.925 so was probably taken up to 0.975 during flutter tests. I've personally been at 0.96 in a Falcon during a test flight. The Boeing structures, particularly around that time, were built to be very strong. There was less computer modelling and less CFD. I can't immediately think of a Boeing ever suffering a structural failure.

CFD is computational fluid dynamics.

If you would like to challenge this, I can give you this test pilots email and feel free to tell him your opinions. Good luck with that. Before you go off on your usual strawman tactics, he is referring to any Boeing crashing, primarily due to structural failure.

I generally do not approve of arguing from authority, but this is a FA18 fighter pilot who duxed his Empire Test Pilots Course, is a current 767 Captain with over 12000 hours and experience on over 130 types. He is a consultant test pilot to this day.

He has confirmed to me what the regulations are for. That Vd is an airspeed selected from a regulatory relationship to Vc. It is the furthest part of the flight envelope that is required to be shown as safe, with regulatory load factor margins, gust factor margins and controllability, primarily after a high speed upset.

It is NOT related in any way to the structural point of failure.

So when are you going to re-edit your erroneous video and provide the correct interpretation of Vd?
 
C.V.

External Quote:
Consultant Experimental and Engineering Test Pilot to the civil and government sectors for more than 20 years. 10 years experience as Regulatory Agency Certification Test Pilot on Part 23 and Part 25 types. Experienced in FAR 23 and 25 certification and audit. Approved by the Airworthiness Agencies of Australia and New Zealand to conduct experimental test flying on all fixed wing aircraft types including Air Transport, Multi-Engine Turboprop and Single-Engine types. Conducted maiden flight of new prototype turbine aircraft and initial development flights in support of FAR Part 23 Certification. Experienced in modification of civil executive jet aircraft to Military Support Role for Target Towing and Electronic Warfare Roles.

Member of the Society of Experimental Test Pilots, Lancaster California USA.

More than 12,000 hours on more than 130 aircraft types.

91ec1e8a90cd6a1984a58f7a2c0fd226.png

Captain, Boeing 767
Qantas
August 1995 – Present (18 years 9 months)Melbourne Area, Australia
Current Boeing 767 Captain. Previous types include A330, 737NG, Boeing 747-400. Approved test pilot for post-maintenance test flights. Project pilot for iPad EFB cockpit integration. Conducted EMC test flights for all aircraft in Qantas fleet.

70d64c26f19816388ca55c1e3302187b.png

Experimental and Engineering Test Pilot
Royal Australian Air Force
July 1982 – November 1995 (13 years 5 months)Aircraft Research and Development Unit
Fighter Pilot F/A-18 and Test Pilot for Fixed Wing aircraft. Senior Fixed-Wing Test Pilot RAAF 1993-1995. Store certification, aircraft evaluation and modification tests for all RAAF fast-jet types. Lead test pilot for evaluation of contenders for jet trainer replacement project. Performed evaluation of seven contender aircraft.

Organizations
Society Of Experimental Test Pilots
Member
December 1995 – Present
Honors & Awards
McKenna Trophy
Empire Test Pilot School
December 19XX
Awarded the JFX McKenna Trophy as Overall Best Student on Number XX Course 19XX.
 
So when are you going to re-edit your erroneous video and provide the correct interpretation of Vd?

I'd also like to see a response, in addition to member "SpaceCowboy", others from the list at "pilotsfor911truth.org". To wit:

External Quote:
CORE MEMBERS LISTED IN THE ORDER IN WHICH THEY JOINED.
LIST UPDATED REGULARLY.


(MY highlight emphasis...carrying on):


External Quote:
Captain Russ Wittenberg (ret)
30,000+ Total Flight Time
707, 727, 737, 747, 757, 767, 777, DC-8, L-1049, Learjet 24/25, L-188
Ground Instructor, Advanced Ground Instructor, Instrument Instructor, Flight Engineer Turbojet
Aircraft Dispatcher
Pan Am, United
United States Air Force (ret)
Over 100 Combat Missions Flown
Command time in:
- N591UA (Aircraft dispatched as United 93)
- N612UA (Aircraft dispatched as United 175)

Captain Ross Aimer
United Airlines, Retired
B-777/767/757/747/737/727/720/707, DC-10/-9/-8 Type ratings
Command time in:
- N591UA (Aircraft dispatched as United 93)
- N612UA (Aircraft dispatched as United 175)

John Lear
Son of Bill Lear
(Founder, creator of the Lear Jet Corporation)
More than 40 years of Flying
19,000+ TT
23 Type ratings
Flight experience includes 707, DC-8, 727, L10-11


Jeff Latas
-Over 20 years in the USAF
--USAF Accident investigation Board President
--Aeronautical Engineer
--Flew the F-111, T38, and F-15E
--Combat experience in the F-15E includes Desert Storm and four tours of duty in Northern and Southern Watch
--Weapons Requirements Officer, USAF HQ, Pentagon
--Standard and Evaluations Flight Examiner, Command level
-Currently Captain for JetBlue Airways

Guy S. Razer, LtCol, USAF (Ret)
3,500+ Hours Total Flight Time
F-15E/C, F-111A/D/E/F/EF, F-16, F-18, B-1, Mig-29, SU-22, T-37/38, Various Cvilian Prop
Combat Time: Operation Northern Watch
USAF Fighter Weapons School Instructor
NATO Tactical Leadership Program Instructor/Mission Coordinator
USAF Material Command Weapons Development Test Pilot
Combat Support Coordination Team 2 Airpower Coordinator, South Korea
All Service Combat Identification Evaluation Team Operations Officer
Boeing F-22 Pilot Instructor
MS Aeronautical Studies, Embry-Riddle Aeronautical University

Dwain Deets
MS Physics, MS Eng
Former Director, Aerospace Projects, NASA Dryden Flight Research Center
Served as Director, Research Engineering Division at Dryden
Recipient of the NASA Exceptional Service Award
Presidential Meritorious Rank Award in the Senior Executive Service (1988)
Selected presenter of the Wright Brothers Lectureship in Aeronautics
Associate Fellow - American Institute of Aeronautics and Astronautics (AIAA)
Included in "Who's Who in Science and Engineering" 1993 - 2000
Former Chairman of the Aerospace Control and Guidance Systems
- Committee of the Society of Automotive Engineers
Former Member, AIAA Committee on Society and Aerospace Technology
37 year NASA career

Lt. Colonel Shelton F. Lankford
United States Marine Corps (ret)
A-4 Skyhawk, KC-130 (10,000+ Hours)
S-2, T-1, F9F, F-11, OV-10, T-2J
303 Combat Missions

Captain Paul A. Trood
B737-800/400 Captain
Qantas Airways
Australia
Experience: 18,000 flight hours


Jim Mustanich
ATP 20,000+ hours
Typed in CE-500, DHC-7, EMB-110, BA-3100
Aircraft flown include Boeing 727,737, Douglas DC-9, MD-80
United Air Lines, American International Airlines, Air Pacific Airlines, West Air Airlines
6-7 years corporate flying in Cessna Citations
Factory demo pilot for Cessna Citations

Ted Muga
Naval Aviator - Retired Commander, USNR
A/C experience - Grumman E-1 and E-2 ( Approx, 3800 hours )
Pan American World Airways - Retired Dec. 1991 ( that's when PanAM went bankrupt )
Flight Engineer/First Officer -- Boeing 707 & Boeing 727 ( approx. 7500 hours )
(I highlighted one that I thought was interesting to point out.....).

I am ALSO very, very interested to know if these people cited by "pilotsfor911truth" still cling to their original claims, and support the "organization" fully, as it has developed.
 
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TWCobra said:

So when are you going to re-edit your erroneous video and provide the correct interpretation of Vd?Click to expand...
I'd also like to see a response, in addition to member "SpaceCowboy", others from the list at "pilotsfor911truth.org". To wit:
hopefully you guys aren't holding your breath! he's been pushing this diagram since at least 2010 (tiffanyinla above top secret vd diagram).
 
It seems that SpaceC is objecting that this is to apply for the condition that the aircraft be in level flight and maintaining a constant Mach number, and that the descent of flight 175 and the manouvering of flight 175 negates the effect of the 20% margin contained in the regulations.

I say that "it seems" to be his objection because he has not actually stated it. Instead he has simply repeated the phrase "constant Mach number and constant altitude" and cast ad homs attacks on those who do not simply succumb to his assertion that this disproves Mick, TWC, WW, and KB.
An admission from P4T about an error such as this is regarded in some circles as one of the signs of the apocalypse....

So... No... I am not holding my breath..
Seems I might as well breath now before expecting a reply to my post. SpaceC says he wants to lead people to the answer rather than just come out and explain it.
OK, well, in my post above I outlined what, it seems to me, he is getting at. Weed Whacker countered, saying that this is not a factor..
Yet SpaceC utterly refuses to address this. Is the above supposition of mine as to his objection, correct? If not , what is his constant reference to the phrase to signify? If I am correct then in what way does the reg's mention of constant mach number and altitude negate the 20% for an aircraft under a moderate g load and shallow dive?
To this layman's view, the constant altitude part is moot since gross exceeding of Vd occurred through only a few thousand feet anyway, iirc.

Furthermore this thread is replete with examples of aircraft that grossly exceeded Vd. The latest being a 727 that barrel rolled twice, hit 0.96 M and 8 g load and held together enough to keep flying. This is a much greater out of the envelope digression than flight 175 experienced. So it would appear encumbant upon PfT to explain why they claim the wings of flight 175 should have broken off.

I shall wait, but I will keep drawing breath. In fact the only time I may skip a breath is if SpaceC actually responds.
 
Despite PFT's kvetching about "real pilots" we have one described by TWC above, who completely contradicts PfT. TWC has invited Balsamo to contact this real pilot.

What is the status of that? Has the invitation been accepted? Has a conversation begun?

SpaceC invites TWC to post at the PfT forum. Is that to be in any subforum there, or strictly in the one specifically reserved for all discussion contradictory to PfT doctrine?
 
Flight 841 reached a max mach of 0.96M and experienced max of 8 g load, and suffered severe damage yet was returned to controlled flight and landed.

What is the Md of a 727?
Or the Vd? This aircraft descended through 34000 feet in 33 seconds. Its average velocity downwards is in the range of 700 mph.
All of the above stats are directly from the NTSB report and the data from the FDR on the flight. The PDF of the report is easily found by a minute of searching. Inexplicably, SpaceC denies these stats outright.
I do not intend to suggest that the 0.96M and 8 g load occurred at the same time. Maybe they did, maybe , probably, not.
It says the planed "rolled through 360 degrees" twice. While not in level flight at the time, this is still a "barrel roll" is it not?

However, I ask these questions only as an aside. The real question, unaddressed, indeed ignored, by PfT and SpaceC, is : exactly how does the constant mach number & constant altitude reference in the Vd+20% regulation bolster the PfT claim that the aircraft should have suffered massive destructive flutter and chase the wings to snap off as per claims and animations from PfT?
 
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Inexplicably, SpaceC denies these stats outright.

Indication of a pattern displayed in other claims from the PfT. Denial of authoritative agencies' (and qualified experts') data, reports, and conclusions. (Such as thoroughly discounting the FDR from American 77...but oddly, not from United 93?)
 
Mick West said:
All you have to do is actually address the issue of flutter past Vd. You can't claim something is wrong, and then not explain why, only hint and insult.

I have already explained why you are wrong using the FAR you sourced while giving you calculations and instruction proving you are wrong. You just didn't like the answer and continue to censor. You will continue your pointless censorship since the answers are not to your liking and repeatedly prove you wrong. Your censorship is pointless due to the fact people are reading my posts no matter where they are.... in your "Rambles" section, or at the P4T forum.

Another great example which proves you wrong is in the alleged text from TWC's "Test Pilot" regarding the A380. I have referenced it many times for you, weedwhacker has even posted the video above, and now the "Test Pilot" has also made reference.

.96 Mach is Vd/Md for the A380. Not "Vd+20%". You can watch the Pilots visibly shaking in their seats due to the onset of flutter as they approach the aircraft Vd/Md. In fact, the airplane broke at .93 Mach, the flutter test had to be aborted, the airplane was then modified, and then the test resumed to certify the airplane to Vd/Md.

Again, scroll to the bottom of this page and learn....
http://theflyingengineer.com/tag/vdmd/

... and actually watch the video...
 
Your flying engineer, is not a test pilot. You can easily confirm my source if you wish, but once again I am not holding my breath because he would demolish your arguments.

"P4T", time to retire gracefully from the argument and reassess your position.
 
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