A question on Airbus landings

[[email protected]]

I've heard that in FBW Airbuses, if your sink rate on finals is low for
whatever reason, the computers might not consider it to be a landing at
all, and might actually prevent reverser deployment and even inhibit
brake application on the landing roll?

Thanks in advance,

Ramapriya

[Dave S]

Google the term "Radar Altimeter"

wrote:
> I've heard that in FBW Airbuses, if your sink rate on finals is low for
> whatever reason, the computers might not consider it to be a landing at
> all, and might actually prevent reverser deployment and even inhibit
> brake application on the landing roll?
>
> Thanks in advance,
>
> Ramapriya
>

[[email protected]]

> wrote:
> > I've heard that in FBW Airbuses, if your sink rate on finals is low for whatever reason,
> > the computers might not consider it to be a landing at all, and might actually prevent
> > reverser deployment and even inhibit brake application on the landing roll?
> >
Dave S wrote:
> Google the term "Radar Altimeter"


I assume that I didn't convey myself adequately because I wasn't asking
about what the aircraft use in detecting terrain.

My question was if in a low sink rate situation - possibly a flatter
profile during finals (a no-flaps situation) or you came in slower and
touched down gently at the initial section of the touchdown roll, does
FBW technology prevent reverser deployment until too late? When I first
read about it, it struck me as the exact opposite of a safety feature
(if at all it's that) because these are the situations when you'd need
reversers the most. I also similary wondered about brakes too, and
whether onboard computers can (or do) inhibit application in some
circumstances.

And I hope this isn't what happened yesterday at Irkutsk.

Ramapriya

[Thomas Borchert]

> I've heard that in FBW Airbuses, if your sink rate on finals is low for
> whatever reason, the computers might not consider it to be a landing at
> all, and might actually prevent reverser deployment and even inhibit
> brake application on the landing roll?
>

You may be referring to the accident in Warsaw some years back. It was
the gear switches that didn't report landing, IIRC. It makes absolutely
no sense to connect landing detection to sink rate on final.

As for the incident in Russia yesterday, the A310 is not FBW.

--
Thomas Borchert (EDDH)

[Thomas Borchert]

> And I hope this isn't what happened yesterday at Irkutsk.
>

Repeat after me: Not all Airbusses are FBW. Not all Airbusses are
FBW...

Besides that, no, your scenario is not a valid one.

--
Thomas Borchert (EDDH)

[Beavis[_1_]]

In article >,
"karl gruber" > wrote:

> No transport certifed jet made requires thrust reverse to stop in the
> distance calculated by the crew for every landing.

That's incorrect.

http://www.ntsb.gov/Recs/letters/2006/A06_16.pdf

"The FAA allows the reverse thrust credit to be used in calculating en
route operational landing distances for some transport-category
airplanes, such as the accident airplane, a 737-700."


The 737-700 that ran off the runway in Chicago this past winter
absolutely used thrust reverse in its landing distance calculation.
They calculated 560 feet of runway remaining after that landing *with*
the Thrust Reversers used. Between the inability to activate the TRs
right away, and the braking action being much poorer than reported to
the crew, it (obviously) wasn't enough runway.

As a result of that accident, I wouldn't be surprised to see the
factoring of the TRs into the data removed or reduced. (The 737-300,
for example, doesn't include the TRs in its landing data.)

[The Visitor]

karl gruber wrote:

> No transport certifed jet made requires thrust reverse to stop in the
> distance calculated by the crew for every landing.

Never say never. Those days are gone.

[karl gruber[_1_]]

I guess I've been retired too long for all that new stuff!



"Beavis" > wrote in message
...
> In article >,
> "karl gruber" > wrote:
>
>> No transport certifed jet made requires thrust reverse to stop in the
>> distance calculated by the crew for every landing.
>
> That's incorrect.
>
> http://www.ntsb.gov/Recs/letters/2006/A06_16.pdf
>
> "The FAA allows the reverse thrust credit to be used in calculating en
> route operational landing distances for some transport-category
> airplanes, such as the accident airplane, a 737-700."
>
>
> The 737-700 that ran off the runway in Chicago this past winter
> absolutely used thrust reverse in its landing distance calculation.
> They calculated 560 feet of runway remaining after that landing *with*
> the Thrust Reversers used. Between the inability to activate the TRs
> right away, and the braking action being much poorer than reported to
> the crew, it (obviously) wasn't enough runway.
>
> As a result of that accident, I wouldn't be surprised to see the
> factoring of the TRs into the data removed or reduced. (The 737-300,
> for example, doesn't include the TRs in its landing data.)

[John Clear]

In article m>,
> wrote:
>
>I assume that I didn't convey myself adequately because I wasn't asking
>about what the aircraft use in detecting terrain.
>
>My question was if in a low sink rate situation - possibly a flatter
>profile during finals (a no-flaps situation) or you came in slower and
>touched down gently at the initial section of the touchdown roll, does
>FBW technology prevent reverser deployment until too late? When I first
>read about it, it struck me as the exact opposite of a safety feature
>(if at all it's that) because these are the situations when you'd need
>reversers the most. I also similary wondered about brakes too, and
>whether onboard computers can (or do) inhibit application in some
>circumstances.
>

I think you are referring to an A320 accident that happened awhile back.

http://www.savive.com.au/casestudy/warsawa320.html and
http://sunnyday.mit.edu/accidents/warsaw-report.html have the details.

Basically, it landed fast, and with a tailwind, didn't get weight
on the wheels, and the runway was wet so the wheels didn't spin
up, but hydroplaned instead. Weight on wheels is needed for thrust
reversers to be enabled, and wheel spin is needed for brakes.

This accident, and many many similar ones, are pilot training issues
more then aircraft systems issues.

John
--
John Clear - http://www.clear-prop.org/

[Al[_1_]]

Karl, I think you are talking about the landing calculations for a
destination or alternate, prior to takeoff, and are correct.

Beavis is correct for a "prior to landing calculation".

Al G



"karl gruber" > wrote in message
...
>I guess I've been retired too long for all that new stuff!
>
>
>
> "Beavis" > wrote in message
> ...
>> In article >,
>> "karl gruber" > wrote:
>>
>>> No transport certifed jet made requires thrust reverse to stop in the
>>> distance calculated by the crew for every landing.
>>
>> That's incorrect.
>>
>> http://www.ntsb.gov/Recs/letters/2006/A06_16.pdf
>>
>> "The FAA allows the reverse thrust credit to be used in calculating en
>> route operational landing distances for some transport-category
>> airplanes, such as the accident airplane, a 737-700."
>>
>>
>> The 737-700 that ran off the runway in Chicago this past winter
>> absolutely used thrust reverse in its landing distance calculation.
>> They calculated 560 feet of runway remaining after that landing *with*
>> the Thrust Reversers used. Between the inability to activate the TRs
>> right away, and the braking action being much poorer than reported to
>> the crew, it (obviously) wasn't enough runway.
>>
>> As a result of that accident, I wouldn't be surprised to see the
>> factoring of the TRs into the data removed or reduced. (The 737-300,
>> for example, doesn't include the TRs in its landing data.)
>
>

[[email protected]]

Thomas Borchert wrote:
> > I've heard that in FBW Airbuses, if your sink rate on finals is low for
> > whatever reason, the computers might not consider it to be a landing at
> > all, and might actually prevent reverser deployment and even inhibit
> > brake application on the landing roll?
> >
>
> You may be referring to the accident in Warsaw some years back.

Yes Thomas, I was.

> It was the gear switches that didn't report landing, IIRC. It makes absolutely
> no sense to connect landing detection to sink rate on final.

Pardon my ignorance but aren't the two connected, in the sense that
you'd touch down lightly if your sink rate is lower?

Ramapriya

[Thomas Borchert]

> Pardon my ignorance but aren't the two connected, in the sense that
> you'd touch down lightly if your sink rate is lower?
>

Yes, but if you are down, you are down, i.e. the gear is compressed by
the weight of the plane. The problem in Warsaw was that the wheels
didn't start spinning because of aqua planing.

And just to make sure the point gets across: The Airbus 300 and 310
(the early models) are not FBW. The 320 and its derivatives, as well as
the 330 and 340 (and 380) are. As is the Boeing 777.

--
Thomas Borchert (EDDH)

[Big John]

The switch on a main gear strut is called the "Squat Switch". It's
position is used for lots of things on airplane. Pilot can by pass the
"squat" switch if needed in cockpit, ie bypass the "Squat" switch to
pull the gear up on the ground.

Haven't seen the wiring diagram but would guess that reverse thrust
would not be available until you had activation of "Squat" switch, ie
no reverse thrust until you are on the ground.

All the current birds have ASB. Failure in that system (very rare)
prevents any braking.

Lots of what ifs.

Big John

`````````````````````````````````````````````````` ````````````````````

On Mon, 10 Jul 2006 13:46:20 +0200, Thomas Borchert
> wrote:

>> I've heard that in FBW Airbuses, if your sink rate on finals is low for
>> whatever reason, the computers might not consider it to be a landing at
>> all, and might actually prevent reverser deployment and even inhibit
>> brake application on the landing roll?
>>
>
>You may be referring to the accident in Warsaw some years back. It was
>the gear switches that didn't report landing, IIRC. It makes absolutely
>no sense to connect landing detection to sink rate on final.
>
>As for the incident in Russia yesterday, the A310 is not FBW.

[The Visitor]

Big John wrote:


> Haven't seen the wiring diagram but would guess that reverse thrust
> would not be available until you had activation of "Squat" switch, ie
> no reverse thrust until you are on the ground.
>

It doesn't sense wheel spin up?

[Thomas Borchert]

The,

> It doesn't sense wheel spin up?
>

On the 320, it does.

--
Thomas Borchert (EDDH)

[The Visitor]

That was my point.

Thomas Borchert wrote:

> The,
>
>
>>It doesn't sense wheel spin up?
>>
>
>
> On the 320, it does.
>

[Capt.Doug]

>"Beavis" wrote in message > As a result of that accident, I wouldn't be
surprised to see the
> factoring of the TRs into the data removed or reduced. (The 737-300,
> for example, doesn't include the TRs in its landing data.)

That landing data calculation was allowed by Ops Specs, which have been
revoked at most carriers.

D.

[Big John]

If your sitting on ramp in a 320 and put the gear handle in the up
position will the gear retract? (No wheel spin)

Wheel spin up might be used to prevent reverse thrust being applied
while airborne??? If so, how can reverse thrust be used to back the
aircraft into a parking spot?

I'm asking questions, not critizing.

Many thing have changed snce my last hands on on heavy iron.


Big John
``````````````````````````````````````````````

On Wed, 12 Jul 2006 10:39:31 -0400, The Visitor
> wrote:

>That was my point.
>
>Thomas Borchert wrote:
>
>> The,
>>
>>
>>>It doesn't sense wheel spin up?
>>>
>>
>>
>> On the 320, it does.
>>