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NASA Shuttle Specific Sections => Atlantis (Post STS-135, T&R) => Topic started by: edkyle99 on 06/24/2007 05:46 pm

Title: STS-117 Landing Gear Slow to Drop?
Post by: edkyle99 on 06/24/2007 05:46 pm
I saw an Aviation Week headline that said "Atlantis Had Slow Landing Gear".  I couldn't access the online story, but I did notice that the right main gear looks slow to drop in this video.

http://www.youtube.com/watch?v=x3krq1IGyoY

 - Ed Kyle
Title: Re: STS-117 Landing Gear Slow to Drop?
Post by: psloss on 06/24/2007 05:52 pm
I found this link over there (with pix from Bill Hartenstein):
http://www.aviationweek.com/aw/blogs/space/index.jsp?plckController=Blog&plckBlogPage=BlogViewPost&newspaperUserId=04ce340e-4b63-4d23-9695-d49ab661f385&plckPostId=Blog%3a04ce340e-4b63-4d23-9695-d49ab661f385Post%3a9f5b1025-5de8-47b4-8ec3-fed2103e151a&plckScript=blogScript&plckElementId=blogDest

The blog post says in part:
Quote
There is no indication of any problem with the Atlantis gear, but NASA and United Space Alliance engineers may inspect the mechanism to assess the slower deployment of the right one.
Title: Re: STS-117 Landing Gear Slow to Drop?
Post by: Andrewwski on 06/24/2007 06:01 pm
It was discussed a bit in the flight day thread, but I don't think anything ever came of it.
Title: Re: STS-117 Landing Gear Slow to Drop?
Post by: ShuttleDiscovery on 06/24/2007 06:09 pm
Ok the right one was a little slower, but as long as they're down and locked by the time they hit the runway  ;)   then there isn't really much to be concerned about...
Title: Re: STS-117 Landing Gear Slow to Drop?
Post by: DaveS on 06/24/2007 06:11 pm
Quote
psloss - 24/6/2007  7:52 PM

I found this link over there (with pix from Bill Hartenstein):
http://www.aviationweek.com/aw/blogs/space/index.jsp?plckController=Blog&plckBlogPage=BlogViewPost&newspaperUserId=04ce340e-4b63-4d23-9695-d49ab661f385&plckPostId=Blog%3a04ce340e-4b63-4d23-9695-d49ab661f385Post%3a9f5b1025-5de8-47b4-8ec3-fed2103e151a&plckScript=blogScript&plckElementId=blogDest

The blog post says in part:
Quote
There is no indication of any problem with the Atlantis gear, but NASA and United Space Alliance engineers may inspect the mechanism to assess the slower deployment of the right one.
Now that you mention it, I had heard the same thing in an old video I have downloaded from InsideKSC of KSC being prepped for hurricane Frances. In that video you could see that MLGs and NLG being retracted.

I have attached an MP3 of the MLG doors slamming shut, where you can really hear the delay between the left and right doors being closed.

There's a whopping 1.25 second difference between both doors, with the right MLG door closing first and the left door closing last.
Title: Re: STS-117 Landing Gear Slow to Drop?
Post by: ShuttleDiscovery on 06/24/2007 06:14 pm
Is that MP3 of Atlantis' gear or another orbiter?
Title: Re: STS-117 Landing Gear Slow to Drop?
Post by: DaveS on 06/24/2007 06:20 pm
Quote
ShuttleDiscovery - 24/6/2007  8:14 PM

Is that MP3 of Atlantis' gear or another orbiter?
I believe it's Atlantis.
Title: Re: STS-117 Landing Gear Slow to Drop?
Post by: STS Tony on 06/24/2007 07:10 pm
I suppose this isn't a biggy, so long as they lock into place.
Title: Re: STS-117 Landing Gear Slow to Drop?
Post by: USFJoseph on 06/24/2007 09:15 pm
Which raises the question -- what if they don't lock into place?  What is the plan?  Glide as long as possible and make a belly landing?  I suppose that's about all they can do with the decision basically being to glide or to put her down quickly...
Title: Re: STS-117 Landing Gear Slow to Drop?
Post by: steve_slitheen on 06/24/2007 10:11 pm
Quote
USFJoseph - 24/6/2007  10:15 PM

Which raises the question -- what if they don't lock into place?  What is the plan?  Glide as long as possible and make a belly landing?  I suppose that's about all they can do with the decision basically being to glide or to put her down quickly...

It's not really like they have any option at this point - real split second timing between realising the gear's not locked and doing something about it.  They can't abandon the landing attempt, but might just be able to react to minimise the damage.  I guess it would really be Game Over for that particular orbiter.
Title: Re: STS-117 Landing Gear Slow to Drop?
Post by: iphitus on 06/24/2007 10:26 pm
Isnt there some sort of explosive charge or bolts to force the door open in case of a door issue? That provides redundancy for one possible problem, but I suppose there's not much you can do if the gear itself flat out fails.
Title: Re: STS-117 Landing Gear Slow to Drop?
Post by: JonSBerndt on 06/24/2007 11:01 pm
I wonder if it would be prudent in this case to deploy the shoot immediately at first contact? That would serve the purpose of helping to keep the orbiter aligned straight w.r.t. the runway, and also to *perhaps* assist in slowing slapdown.

Jon
Title: Re: STS-117 Landing Gear Slow to Drop?
Post by: USFJoseph on 06/24/2007 11:49 pm
I also imagine the procedure (I assume there is one) depends on the location.  Say it's KSC they can glide farther (maybe) and belly land in the swamp vs the concrete as opposed to say Edwards?
Title: Re: STS-117 Landing Gear Slow to Drop?
Post by: yinzer on 06/25/2007 12:08 am
I don't think that the orbiter will survive a belly landing.  The trailing edge hits the ground first and slams the nose down hard enough to break things.
Title: Re: STS-117 Landing Gear Slow to Drop?
Post by: Namechange User on 06/25/2007 12:43 am
The orbiter would not survive a belly landing.  Glide slope and landing speeds are much steeper and higher, respectively. than a regular aircraft.  

The gear have "thrusters" on them as well.  This is what they are called but do not think of them as the rocket-type thrusters.  They provide an extra push to extend the gear if necessary.  

As for deploying the chute pre-touchdown, that would be a bad idea.  The was concerns this was going to happen on STS-95 during approach the scenerios were not good as I recall.  This was the flight where the door fell off at launch.
Title: Re: STS-117 Landing Gear Slow to Drop?
Post by: DaveS on 06/25/2007 12:47 am
Quote
OV-106 - 25/6/2007  2:43 AM
This was the flight where the door fell off at launch.
And hit SSME#1.
Title: Re: STS-117 Landing Gear Slow to Drop?
Post by: shuttlefan on 06/25/2007 01:22 am
Quote
ShuttleDiscovery - 24/6/2007  1:09 PM

Ok the right one was a little slower, but as long as they're down and locked by the time they hit the runway  ;)   then there isn't really much to be concerned about...

But we have to wonder if the hardware is trying to tell them something. Remember what Ron Dittamore (Space Shuttle Program Manage at the time of STS-107), said about always listening to the hardware?
Title: Re: STS-117 Landing Gear Slow to Drop?
Post by: Namechange User on 06/25/2007 01:56 am
Quote
shuttlefan - 24/6/2007  8:22 PM

Quote
ShuttleDiscovery - 24/6/2007  1:09 PM

Ok the right one was a little slower, but as long as they're down and locked by the time they hit the runway  ;)   then there isn't really much to be concerned about...

But we have to wonder if the hardware is trying to tell them something. Remember what Ron Dittamore (Space Shuttle Program Manage at the time of STS-107), said about always listening to the hardware?

Well why he may have said it publically, that was not something where we all said, "yeah, you're right.  Why didn't we think of that."  There are a multitude of inspections, OMRS File 9 requirements for mechanisms, hyd, etc.  Plus the gear gets cycled multiple times during a flow.  The vehicle just landed on Friday and since there were no major issues most of the engineering teams, except those in Ground Ops at EAFB, have had the weekend off.  

Lets not go looking for an issue either.  If there's something we'll find it and fix it.
Title: Re: STS-117 Landing Gear Slow to Drop?
Post by: rdale on 06/25/2007 01:57 am
What would the "hardware" be "saying" in this instance?
Title: Re: STS-117 Landing Gear Slow to Drop?
Post by: psloss on 06/25/2007 10:23 am
To some extent, I think this is a case of more eyeballs getting a closer look at landing gear deploy.  If Atlantis had landed at night and/or at KSC, I'm not sure this would have been particularly noticeable from the NASA TV broadcast.  It's been a long time since an Edwards daytime landing -- the previous landing (STS-114) was in darkness.  Before that, the previous landings (both daytime) at Edwards were STS-111 in June, 2002, and STS-100 in May, 2001.
Title: Re: STS-117 Landing Gear Slow to Drop?
Post by: gordo on 06/25/2007 12:03 pm
This is very interesting.

I assume the gear is electrically signaled to deploy.  The GPCs should be able to show when the signal was sent compaired to the other gear.  

I actually wonder if a "non-deploy" message came back and it was sent again, or one of the back up systems were signaled.  With the design of the system it would be very hard to get this sort of lag unless something had gone a bit wrong somewhere.
Title: Re: STS-117 Landing Gear Slow to Drop?
Post by: shuttlefan on 06/25/2007 01:45 pm
Quote
rdale - 24/6/2007  8:57 PM

What would the "hardware" be "saying" in this instance?

It would POSSIBLY be saying: "I have a more serious problem and you had better check to make sure it's not a generic problem that could be more serious on future landings." ;)
Title: RE: STS-117 Landing Gear Slow to Drop?
Post by: johng on 06/25/2007 02:08 pm

You know, after I read this thread, I spent some time on youtube looking at landing videos and regardless of orbiter or mission, they all have some time lag between the two mains, with the right one deploying last.  Looks like a non-event to me.
Title: RE: STS-117 Landing Gear Slow to Drop?
Post by: psloss on 06/25/2007 02:28 pm
Quote
johng - 25/6/2007  10:08 AM


You know, after I read this thread, I spent some time on youtube looking at landing videos and regardless of orbiter or mission, they all have some time lag between the two mains, with the right one deploying last.  Looks like a non-event to me.
Out of curiosity, which landings did you find?  I was thinking of posting just the deploy sequence from the last handful of Edwards landings for illustrative purposes (and FWIW, I'm seeing the same thing as you).
Title: RE: STS-117 Landing Gear Slow to Drop?
Post by: johng on 06/25/2007 02:43 pm

I dunno. Just some surfing before bed last night...
Title: Re: STS-117 Landing Gear Slow to Drop?
Post by: JWag on 06/25/2007 03:23 pm

Quote
DaveS - 24/6/2007  1:11 PM  

I have attached an MP3 of the MLG doors slamming shut, where you can really hear the delay between the left and right doors being closed.  There's a whopping 1.25 second difference between both doors, with the right MLG door closing first and the left door closing last.

If I'm not mistaken, the MLG and NLG are deployed entirely by gravity, and are incapable of retracting themselves.  I don't have Dennis Jenkins' book in front of me, but I'm mostly certain that I've read that locking the gear in place and locking the doors shut is done entirely by workers.  It wouldn't surprise me that there was a delay.

It makes some sense - why have the weight and complexity of all the hydraulics to retract the landing gear, when it will only ever need to be done while workers were swarming over the vehicle anyway?

It would seem reasonable for there to be a specification that defines the maximum allowable time from when gear deploy is signaled to receipt of signals that it is down and locked.  This could be tested in the OPF (though without benefit of a ~200 knot wind).
Title: Re: STS-117 Landing Gear Slow to Drop?
Post by: Namechange User on 06/25/2007 03:50 pm
The gear is deployed by the crew.  That is one of the reasons the orbiter cannot fly completely automated.  There are two switches that need to be thrown.  The gear is gravity assisted but hydraulically driven.
Title: RE: STS-117 Landing Gear Slow to Drop?
Post by: mkirk on 06/25/2007 04:29 pm
Here is a public link to a section of the SCOM that describes landing gear deployment for the orbiter.

http://www.shuttlepresskit.com/scom/214.pdf

Page 2 discusses the deployment sequence.

I am just hearing about this issue since I have been traveling since Friday so I can’t confirm anything yet or offer any educated comments.

I will say that “IF” the deploy times for any of the gear were really “out of family”, this issue MUST be well understood prior to the next flight.  So no matter how easy or hard it is to get a handle on this it will be talked about in excruciating detail within the program as they head into the 118 flight readiness review.

Mark Kirkman

Title: Re: STS-117 Landing Gear Slow to Drop?
Post by: JonSBerndt on 06/27/2007 04:20 am
Quote
OV-106 - 24/6/2007  7:43 PM

The orbiter would not survive a belly landing.  Glide slope and landing speeds are much steeper and higher, respectively. than a regular aircraft.  

The gear have "thrusters" on them as well.  This is what they are called but do not think of them as the rocket-type thrusters.  They provide an extra push to extend the gear if necessary.  

As for deploying the chute pre-touchdown, that would be a bad idea.  The was concerns this was going to happen on STS-95 during approach the scenerios were not good as I recall.  This was the flight where the door fell off at launch.

The glide slope doesn't matter - the flare is executed regardless of gear state. I didn't see anyone suggest deploying the chute prior to touchdown. Ground effect might mitigate slapdown a bit, allowing a shallower AOA. Deploying the chute at first contact (given the orbiter CG location and the chute mount point above it) might help reduce slapdown - although there is a delay between chute deploy and full inflation that would probably render that utilization useless.

Jon
Title: RE: STS-117 Landing Gear Slow to Drop?
Post by: mkirk on 07/01/2007 04:21 pm
It should be pointed out that at this point they believe the deployment was “within specs” and therefore not an issue.

As for landing gear up, this was always a sensitive subject in the short time that I worked in training.  The general consensus is that it would be a really bad day especially with a full payload bay like in an ascent abort scenario.
 
There is an established failed tire technique which is intended to help maintain directional control and help keep the orbiter from yawing into the bad tire.  There is no generally accepted, published (i.e. in the FDF checklists) procedure for landing gear up.

Since someone brought up the use of the drag chute I will relate this little story about “none traditional - uncertified uses”.

I was working with one of my senior instructors and John Young in the SMS (shuttle mission simulator) as we looked at some short field landing techniques and capabilities.

I was flying right seat while John was in the left.  On some of the approaches John had me pop the chute while we were crossing the threshold (i.e. still in the air at around 20 feet).  His intent was to have the chute unreefed by the time the main gear hit the runway, thus allowing us to slow down all that much faster.

I told one of my closest friends who happened to work in the MMACS group (mechanical, maintenance, arm, and crew systems) of the mission control center – among their responsibilities are the landing gear and the drag chute systems.  She and her fellow MMACS types were not too happy to hear what we were doing…they thought it was an exceptionally bad idea and began listing the reasons why…In fact current procedures expressly say DO NOT DEPLOY the chute prior to main gear touchdown or above 230 knots.

I should note however, that at least in the SMS, the technique worked well and we were able to perform some very short field landings by combining the early deploy with some other techniques.


Mark Kirkman
Title: Re: STS-117 Landing Gear Slow to Drop?
Post by: gordo on 07/01/2007 05:09 pm
I wonder what were the thoughts going round the MCC when Columbia's telemetry intially reported 2 flat tyres on 107? "this could be an interesting landing?"
Title: Re: STS-117 Landing Gear Slow to Drop?
Post by: psloss on 07/01/2007 05:17 pm
Quote
gordo - 1/7/2007  1:09 PM

I wonder what were the thoughts going round the MCC when Columbia's telemetry intially reported 2 flat tyres on 107? "this could be an interesting landing?"
Bailout, speculatively.  This was discussed in e-mails during the mission and was then extensively reported after the disaster; here's Bill Harwood's story:
http://www.spaceflightnow.com/shuttle/sts107/030226email/

You can find the e-mails here, along with the transcript of the teleconference with JSC flight engineers Bob Doremus and Jeff Kling (Kling was the MMACS officer in the MCC):
http://www.nasa.gov/columbia/media/Media_Resources_Archives.html
Title: Re: STS-117 Landing Gear Slow to Drop?
Post by: gordo on 07/01/2007 05:34 pm
thanks for these, very sobering
Title: Re: STS-117 Landing Gear Slow to Drop?
Post by: brahmanknight on 07/01/2007 06:10 pm
Wow.....those articles are VERY sobering.  Sent chills down my back.  Even if Columbia had made it to Florida, the gear may not have worked.  With such a heavy payload, they would have been doomed in almost any landing possibility.
Title: Re: STS-117 Landing Gear Slow to Drop?
Post by: psloss on 07/01/2007 06:18 pm
Quote
gordo - 1/7/2007  1:34 PM

thanks for these, very sobering
I shouldn't prolong this tangent unless it is disassociated with the unrelated observation that prompted this thread, but if you read the transcript in Harwood's story, they lost the tire pressure measurements (the measurements went off-scale low).  Which isn't the same thing as a "flat."
Title: RE: STS-117 Landing Gear Slow to Drop?
Post by: rkoenn on 07/05/2007 12:43 am
I work mechanisms for NASA on OV-104 which includes the landing gear and tires.  We actually own the mechanism and not the hydraulic systems.  The delta between the left and right main gear was 1.2 seconds but I have heard nothing about any concerns with this.  There are pyro explosives to blow the gear open if the hydraulic systems fail but they have never had to be used from what I know.  Also, there is a large delay between door closures during landing gear retract.  In the early days it was very large and also funny to watch someone uninitiated observe a gear retract.  The gear go up with right going first.  In those days the right would close with the left gear about 80% retracted.  However when the right gear closed completely it would release hydraulic pressure and the left would fall back to about 25% closed which would really freak out anyone not prepared for that to happen right behind their back.  There was a mod done later to the hydraulics to prevent this large pressure drop so the gear actually barely falls at all anymore.  And for those who don't know, the nose gear cannot retract and close the doors completely under hydraulics.  Hence there is a broom brigade that uses push brooms wrapped in foam at 4 locations to push the door tightly closed.
Title: RE: STS-117 Landing Gear Slow to Drop?
Post by: psloss on 07/05/2007 09:48 am
Quote
rkoenn - 4/7/2007  8:43 PM

I work mechanisms for NASA on OV-104 which includes the landing gear and tires.  We actually own the mechanism and not the hydraulic systems.  The delta between the left and right main gear was 1.2 seconds but I have heard nothing about any concerns with this.
Thanks.