KCFlyer
Veteran
- Aug 20, 2002
- 11,284
- 1,427
Didn't y'all used to have an ignore button...I'd be glad to utilize it if you tell me how to get to it.
Nevermind....I found it and added my first user to it.
SWA and safety at MDW
- Thread starter magsau
- Start date
Nevermind....I found it and added my first user to it.
BoeingBoy
Veteran
- Nov 9, 2003
- 16,512
- 5,865
- Banned
- #17
USAir757 & magsau,
You both make basically the same point - pilot's must balance known risks on a daily basis to keep overall risk as low as possible.
Admittedly, I used extreme examples to make a point - after all, leaving the airplane at the gate is the safest decision possible. Unfortunately, the aviation industry would come to a halt.
So pilots do what they're paid to do - balance risks to arrive at an acceptable tradeoff - a risk/reward decision if you like.
A less extreme example:
Using balanced T/O thrust (flex, reduced, etc) uses extra runway to allow lower engine wear & tear - an economic benefit. Until the amount of extra runway exceeds the maximum reduction allowed, you're "tricking" the airplane into performing as if it's at maximum T/O weight for that runway - reducing the margin of safety. Yet pilots use reduced T/O thrust daily to obtain economic benefit for their company.
Another mundane example is fuel tankering. Depending somewhat on the situation, the safest choice would probaly be to not tanker - better T/O and landing margins. Yet we tanker daily for an economic benefit, trading a small margin of safety for money.
You both know that the FAA is famous for safety trade-offs, usually under pressure from industry concerning cost. Likewise, we pilots are called on to make trade-offs on a daily basis. That's why they pay us the big bucks.
All I know at this point - from NTSB reports - is that:
1 - The pilots guidance showed them legal to land on that runway that night.
2 - For some reason undetermined at this point, the T/R's didn't deploy till well down the runway.
3 - The NTSB is trying to determine why the deceleration rate was low given the brake pressure applied by autobrakes then manual braking.
4 - The airplane ran off the end of the runway and an innocent bystander was killed.
I'll leave you with a question I touched on in my last post. If you ask any Captain who has just landed on a relatively short, contaminated runway exactly what the margin between stopping distance and runway length was, would they be able to tell you? My guess would be "No", yet they just landed.
You'll note that I have neither praised nor condemned these pilots. The time for that will come once all the facts are in. I suspect that, barring finding some mechanical fault, this will end up being pilot error.
Even if that's the case, I personally find it much more productive to learn from their mistake than gloat at their misfortune.
Jim
ps - USAir757, you're right - without speculation there wouldn't be anything to read on these boards
You both make basically the same point - pilot's must balance known risks on a daily basis to keep overall risk as low as possible.
Admittedly, I used extreme examples to make a point - after all, leaving the airplane at the gate is the safest decision possible. Unfortunately, the aviation industry would come to a halt.
So pilots do what they're paid to do - balance risks to arrive at an acceptable tradeoff - a risk/reward decision if you like.
A less extreme example:
Using balanced T/O thrust (flex, reduced, etc) uses extra runway to allow lower engine wear & tear - an economic benefit. Until the amount of extra runway exceeds the maximum reduction allowed, you're "tricking" the airplane into performing as if it's at maximum T/O weight for that runway - reducing the margin of safety. Yet pilots use reduced T/O thrust daily to obtain economic benefit for their company.
Another mundane example is fuel tankering. Depending somewhat on the situation, the safest choice would probaly be to not tanker - better T/O and landing margins. Yet we tanker daily for an economic benefit, trading a small margin of safety for money.
You both know that the FAA is famous for safety trade-offs, usually under pressure from industry concerning cost. Likewise, we pilots are called on to make trade-offs on a daily basis. That's why they pay us the big bucks.
All I know at this point - from NTSB reports - is that:
1 - The pilots guidance showed them legal to land on that runway that night.
2 - For some reason undetermined at this point, the T/R's didn't deploy till well down the runway.
3 - The NTSB is trying to determine why the deceleration rate was low given the brake pressure applied by autobrakes then manual braking.
4 - The airplane ran off the end of the runway and an innocent bystander was killed.
I'll leave you with a question I touched on in my last post. If you ask any Captain who has just landed on a relatively short, contaminated runway exactly what the margin between stopping distance and runway length was, would they be able to tell you? My guess would be "No", yet they just landed.
You'll note that I have neither praised nor condemned these pilots. The time for that will come once all the facts are in. I suspect that, barring finding some mechanical fault, this will end up being pilot error.
Even if that's the case, I personally find it much more productive to learn from their mistake than gloat at their misfortune.
Jim
ps - USAir757, you're right - without speculation there wouldn't be anything to read on these boards
Speaking of speculation, point #2 jumps out at me. I'm wondering if the RA TR lockout malfunctioned? If it had, the TR's wouldn't have been able to deploy until late in the rollout. Kinda makes me wonder??????
**Moderator Note: Please refrain from quoting a lengthy post. It just makes it easier for everyone to read follow-on posts. Thank you.**
corl737
Veteran
- Jun 13, 2005
- 565
- 6
Hopefully the NTSB has access to the information that will reveal the true mechanical status of the TRs. Too bad they don't have data recorders for the actual runway conditions, too. :angry:
BoeingBoy
Veteran
- Nov 9, 2003
- 16,512
- 5,865
- Banned
- #20
Hopefully, any mechanical malfunction will be found during the investigation.
Like I've said before, I have absolutely zero experience on the 700 model. However, I've personally had two instances of both T/R's not deploying - fortunately with plenty of runway each time.
The first was on the 737-200 the first landing of my first flight on the real airplane (not sim). The plane had come directly from maintenance for that flight and turned out that a circuit breaker hadn't been reset in the belly (the E&E compartment to be precise).
The other was on the 737-300. Had flown that airplane two legs already with everything normal, then landed and couldn't deploy the T/R's (both I and the F/O tried). Taxiing to the gate, tried them again and on the second attempt they worked. Maintenance could find nothing wrong, so who knows what happened.
Jim
The -200 has different lockouts than the -300's and up. The 200's use the Oil Pressure switch and the AG sensor. On the later models, I know that the RA has an input and the rest escapes me at the moment. As far as the CB goes on the 200...power to the arming valve comes from the BB. Can't think of any CB in the E&E at the moment......Anyway, I'm sure the NTSB will uncover it if the system malfunctioned.
BoeingBoy
Veteran
- Nov 9, 2003
- 16,512
- 5,865
- Banned
- #22
Thanks, peaches. The 200 incident was over 14 years ago so my memory of the circuit breaker location was obviously faulty. FWIW, the 200's had been modified to add the RA as a backup to the oil pressure & AG sensor by the time of my incident. It's always been my understanding that the modification was made as a result of the PI overrun accident in CLT back in the mid-late 80's.
Jim
Jim
- Thread Starter
- Thread starter
- #23
I do believe you are correct that the change was a result of the PI overrun. Also, there were some Auto Spd Brake issues with that accident too if I remember correctly. Didn't they modify the -200's squat switch/zbar to prevent a recorrunce.
BoeingBoy
Veteran
- Nov 9, 2003
- 16,512
- 5,865
- Banned
- #24
Could have - I just don't remember. I just remember the ground school instructors for the 200 stressing the mod to the T/R system.
That accident was the usual chain of events...
1 - Excess speed to a wet runway.
2 - Runway had "ruts" from aircraft main gear causing two "trails" of standing water.
3 - #1 & #2 led to hydroplaning
4 - That led to no wheel spinup
5 - That led to no autospoiler deployment
6 - That led to AG sensor remaining in "air" mode
7 - That led to no reverser deployment
8 - That led to the aircraft ending up off the end of the runway (nose down against the railroad tracks, I might add)
Jim
[edit to add a 2a or 3a that I just remembered]
2a or 3a - runway had excessive rubber buildup in T/D zone which contributed to poor drainage.
That accident was the usual chain of events...
1 - Excess speed to a wet runway.
2 - Runway had "ruts" from aircraft main gear causing two "trails" of standing water.
3 - #1 & #2 led to hydroplaning
4 - That led to no wheel spinup
5 - That led to no autospoiler deployment
6 - That led to AG sensor remaining in "air" mode
7 - That led to no reverser deployment
8 - That led to the aircraft ending up off the end of the runway (nose down against the railroad tracks, I might add)
Jim
[edit to add a 2a or 3a that I just remembered]
2a or 3a - runway had excessive rubber buildup in T/D zone which contributed to poor drainage.
Personally, I would welcome that intervention, as it'd make this board a nicer place to be.
I do, however, see a difference between the primary instigator, and the respondee. There wouldn't be a case of the latter, if the former didn't exist...
Carry on...
KCFlyer
Veteran
- Aug 20, 2002
- 11,284
- 1,427
Moot point OPNL...I found the ignore option, and I am using it. There will be no more banter from me.
The 26 feet remaining to stop was based on braking action poor. The braking action report that the SWA pilots got was braking action fair. Using that data the stopping distance was much more than 26 feet, a whole lot more.
The landing data that SWA uses for the -700 came from Boing and is Boeing's property. SWA isn't allowed to change it. Boeing's data, and how they came up with it, was approved by the FAA. I suppose you want SWA to tell the FAA and Boeing that they are both wrong and SWA is going to do the landing data their own way.
Jim, I remember some chronic problems with T/R's not deploying that used that RA signal to unlock them. It's been a number of years, but I remember something along that line. In any event, I'm certain the crew did everything to be safe.
- Thread Starter
- Thread starter
- #29
Why would CAL have no landings approved at MDW under those conditions? Both using Boeing data and FAA approved, one says yes and the other says no. So yes the operator can massage those numbers to meet its requirements.
Which conditions are you talking about? The one reported by the tower or the actual condition. If you are talking about the actual condition, poor braking and a 9 knot tail wind, then I will inform you that SWA doesn't authorize landing in those conditions. If it was what the tower reported, good braking and a minimal tailwind then even CAL lands at MDW in those conditions.
