A question on Airbus landings

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

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

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

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)

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)

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.)

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.

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.)

In article om,
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/

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.)