Arming Speed Brake On 737
- Thread starter Cfm56
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Atlantic said:
Someone I flew with said they had come from a European 737 operator and they had it in their manual not to arm the speedbrake till AFTER gear extension. Apparently someone in their flight department feared the remote possibility that something could happen to the air/ground sensor during gear extension causing the spoilers to extend. Was just curious if anyone had seen this as I never heard of such a thing till talking to this guy.
N924PS
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Cfm56 said:
The Fokker F100 (remember those RJ's), had a Warning in the Pilot's Handbook regarding Lift Dumper arming. Lift Dumpers are essentially ground spoilers.
Lift dumpers were not to be armed prior to gear extension because of possible inadvertent deployment due to a failure of a sensor system.
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The DC-9 and MD-80 had a restriction like this.
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767jetz
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Many aircraft systems operate using a multiple-logic system. ie: if criteria a, b, and c are met then x,y,z will happen. Depending on what aircraft type, "weight-on-wheels," "truck tilt" or "ground sensing" plays a role in many systems such as anti-skid, ground spoilers, autobrakes, pressurization, and even engine idle speed to name a few. And sometimes manufacturers will update or change the logic of a particular type aircraft in later production runs. So an early 737-300 for example might have a slightly different logic for spoiler operation than a 737-300 built years later.
On the 757/767, if we have an AUTO SPD BRK light we can not arm the speed brakes for landing at all, even with the gear down, and they have to be operated manually after touchdown. This doesn't mean that they wouldn't work properly if armed. It only means that there is a fault in the logic which could affect the redundancy built into the system for safety reasons. Therefore you could be just one more small fault away from having full ground spoilers deployed in flight. (Not a good thing during an approach when low to the ground.)
As for different airlines having different procedures, often the person who wrote the manual for the airline (could have been decades ago in some cases) may have felt it was prudent to have an additional level of redudancy. When the manual is approved by the FAA they make sure that all of the manufacturers required procedures are covered, and if the airline chooses to add additional safety measures, they will usually sign off on it, as long as it is more conservative. Once it has the blessing of the FAA it is written in stone for that airline, and changing it is usually a long and costly process. This is why airlines who fly the same type aircraft have different operating procedures, and you can't just take a pilot from one airline and stick them in another airline's aircraft.
Not to get off on a tangent here, but it is an interesting example of how these differences arise. When TWA first took delivery of the L1011, someone there decided that an overhead switch should be flipped forward for "ON" and backward for "OFF." (I may have that reversed, it's been may years since I was a 1011 engineer.) Anyway, Lockheed designed them the other way, so all of TWA's 1011's were modified to reverse the switch position. The problem becomes obvious when you consider the pilot of another airline coming over and trying to fly a TWA 1011, and flipping all the switches the wrong way! Either the pilots need to be retrained, or the airplanes converted.
Hope this answers your question.
On the 757/767, if we have an AUTO SPD BRK light we can not arm the speed brakes for landing at all, even with the gear down, and they have to be operated manually after touchdown. This doesn't mean that they wouldn't work properly if armed. It only means that there is a fault in the logic which could affect the redundancy built into the system for safety reasons. Therefore you could be just one more small fault away from having full ground spoilers deployed in flight. (Not a good thing during an approach when low to the ground.)
As for different airlines having different procedures, often the person who wrote the manual for the airline (could have been decades ago in some cases) may have felt it was prudent to have an additional level of redudancy. When the manual is approved by the FAA they make sure that all of the manufacturers required procedures are covered, and if the airline chooses to add additional safety measures, they will usually sign off on it, as long as it is more conservative. Once it has the blessing of the FAA it is written in stone for that airline, and changing it is usually a long and costly process. This is why airlines who fly the same type aircraft have different operating procedures, and you can't just take a pilot from one airline and stick them in another airline's aircraft.
Not to get off on a tangent here, but it is an interesting example of how these differences arise. When TWA first took delivery of the L1011, someone there decided that an overhead switch should be flipped forward for "ON" and backward for "OFF." (I may have that reversed, it's been may years since I was a 1011 engineer.) Anyway, Lockheed designed them the other way, so all of TWA's 1011's were modified to reverse the switch position. The problem becomes obvious when you consider the pilot of another airline coming over and trying to fly a TWA 1011, and flipping all the switches the wrong way! Either the pilots need to be retrained, or the airplanes converted.
Hope this answers your question.
767jetz,
Your correct and incorrect and the same time.
You are correct in the fact that at any (major) airline, generally the procedures for the same aircraft will be different at another (major) airline. This is due to different options and perspectives on how to operate the particular aircraft.
This works great with a fleet of aircraft that are common. Unfortunetly, smaller airlines that get aircraft sold from several (major) airlines don't have that luxury.
In my non-sched days, we had a fleet of 727's that came from US, UA, NW, AA, CO, TW, EA, Pan AM and Braniff.
The differences section in our operating manual was as big as the rest of the manual.
I remember the TW birds having the backwards switch position, but remember that's only backwards to everyone but a TW pilot and the rest of the world. Most foriegn carriers aircraft have the switches positioned just like TW aircraft.
Pan Am aircraft had the fire handles on the overhead panel instead of the glare shield. On the fire subject, 727's came with several options on how the fire test worked, depending on where the aircraft came from, depended on how you did the fire test.
Some had auto speed brakes, some didn't...some had auto brakes, some didn't...
Max zero fuel weight, ramp and take-off wieghts were all different. CO birds had digital read-outs on the fuel system. Think it was Braniff birds that had the hydraulic read-outs by the F/O's foot instead of back on the F/E's panel. (been a long time also)
Point being, the aircraft do not need to be converted and standardized. It can be trying at times, but legally, if you have a differences section in your manual, you can fly as many different configurations of the same type aircraft as the manual has listed.
Which means, you can have several operating procedures for the same type aircraft at one airline.
Just my two cents.
Your correct and incorrect and the same time.
You are correct in the fact that at any (major) airline, generally the procedures for the same aircraft will be different at another (major) airline. This is due to different options and perspectives on how to operate the particular aircraft.
This works great with a fleet of aircraft that are common. Unfortunetly, smaller airlines that get aircraft sold from several (major) airlines don't have that luxury.
In my non-sched days, we had a fleet of 727's that came from US, UA, NW, AA, CO, TW, EA, Pan AM and Braniff.
The differences section in our operating manual was as big as the rest of the manual.
I remember the TW birds having the backwards switch position, but remember that's only backwards to everyone but a TW pilot and the rest of the world. Most foriegn carriers aircraft have the switches positioned just like TW aircraft.
Pan Am aircraft had the fire handles on the overhead panel instead of the glare shield. On the fire subject, 727's came with several options on how the fire test worked, depending on where the aircraft came from, depended on how you did the fire test.
Some had auto speed brakes, some didn't...some had auto brakes, some didn't...
Max zero fuel weight, ramp and take-off wieghts were all different. CO birds had digital read-outs on the fuel system. Think it was Braniff birds that had the hydraulic read-outs by the F/O's foot instead of back on the F/E's panel. (been a long time also)
Point being, the aircraft do not need to be converted and standardized. It can be trying at times, but legally, if you have a differences section in your manual, you can fly as many different configurations of the same type aircraft as the manual has listed.
Which means, you can have several operating procedures for the same type aircraft at one airline.
Just my two cents.
UALDC737 said:767,
It wasnt just the 1011. United's 727's had all their switches going the wrong way too compared to TWA.
DC
Former TWA 727 FE/FO
[post="282970"][/post]
A TWA Chief Pilot (or COO, or similar) specified the rocker switches that way for all their aircraft types -- the MD80s also. It was actually a takeover defense -- increase the costs for any acquiring company, who would have to reverse the operation of all the switches to achieve cockpit commonality. Wasn't enough to save them from AA in the end.
767jetz
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smfav8r said:
I agree for the most part. I have a friend who worked at Atlas, and their 747's had many different configurations. However, the FAA still has to sign off on the differences section of the manual. So you can't have unlimited configurations.
At TWA the FAA finally made them split the DC9 and MD80 fleet due to too many differences. At UA the FAA told the company that if they added one more difference to the 757/767 fleet, they would have to split the fleet as well. The 767 fleet had such a big differences section, it was almost as thick as the basic manual. At one point there were something like 5 FMC types and 3 databases alone.
In the long run, standardization decreases training expense and increases safety. I forgot that TWA 727's had the reversed switches as well. (Never was on the 727 at any airline.) But I never heard that it was for self-preservation. That's an interesting factoid.
But back to the speed brake question from the original post, there are many reasons one airline might have a differeent procedure than another.
