Forecasting Arrival Barometer & Descent Forecasting

[Driver170 42]

scandinavian13, on 02 Mar 2016 - 4:47 PM, said:

 

If you land particularly softly, then the weight on wheels sensors might not actually trigger the spoilers

 

Now, I hesitate to disagree with you Kyle, because you know your stuff. However, I'm going to call this one as an old wives' tale -- let's be honest and realistic about it, the WoW sensing relies on MLG shock strut compression as far as I know in the NG. Now, I don't care how gently you touch down, that MLG shock absorber is going to compress. In nearly twenty years of following this hobby I've never yet come across one actual, first-hand account of the spoilers or any other system failing to activate because of a landing so soft the WoW switch didn't activate. However, I'd be delighted to hear one.

 

Personally, my suspicion is that an instructor probably said this to someone once upon a time in order to give a "technical" reason why it's important to prioritise putting it down in the right place over greasing it on, and it's since stuck and become embellished over the years. But, as I say, if anybody can stand it up with personal, first-hand experience then I'm all for it.

 

 

Would have to agree, the thing that reminds me of auto speedbrakes not coming up would be -

 

Bounced Landing

If higher than idle thrust is maintained through initial touchdown, the automatic speedbrake deployment may be disabled even when the speedbrakes are armed. This can result in a bounced landing. During the resultant bounce, if the thrust levers are then retarded to idle, automatic speedbrake deployment can occur resulting in a loss of lift and nose up pitching moment which can result in a tail strike or hard landing on a subsequent touchdown.

[softreset 33]

Man... I wish I could modify the subject line of my original topic.

 

Nonetheless, a lot of great stuff.

[scandinavian13 5,192]

 

 

Personally, my suspicion is that an instructor probably said this to someone once upon a time in order to give a "technical" reason why it's important to prioritise putting it down in the right place over greasing it on, and it's since stuck and become embellished over the years. But, as I say, if anybody can stand it up with personal, first-hand experience then I'm all for it.

 

Perhaps...either way, the greaser is going to result in the weight not settling as quickly to get the spoilers out to dump the lift, and you want to dump the lift ASAP to get more effective braking.

[Spin737 102]

 

 

Now, I hesitate to disagree with you Kyle, because you know your stuff. However, I'm going to call this one as an old wives' tale -- let's be honest and realistic about it, the WoW sensing relies on MLG shock strut compression as far as I know in the NG. Now, I don't care how gently you touch down, that MLG shock absorber is going to compress. In nearly twenty years of following this hobby I've never yet come across one actual, first-hand account of the spoilers or any other system failing to activate because of a landing so soft the WoW switch didn't activate. However, I'd be delighted to hear one.

 

Not a B737, but in a SF340, I did land so softly that the squat switch did not close. We didn't have spoilers, but we did have a lock that would allow you to use reverse once on the ground. Flight Idle Lock. IIRC. Happened once in 6500 hours.

[JoeDiamond 67]

We have a landing "scorecard" we can pull up on the CDU after each landing that will show us various parameters such as max and average descent rate, average N1, max deviation above/below glideslope and a bunch of other stuff.  The parameter I pay the most attention to as I think it gives the best overall assessment of the approach and landing is the seconds from 50' AGL to touchdown.  7-10 seconds is what our check airmen like to see.  Longer and you floated too much, shorter and you didn't flare enough.

[scandinavian13 5,192]

Not a B737, but in a SF340, I did land so softly that the squat switch did not close. We didn't have spoilers, but we did have a lock that would allow you to use reverse once on the ground. Flight Idle Lock. IIRC. Happened once in 6500 hours.

 

Oh slaabs...Dowtys or Hamstands?

 

 

We have a landing "scorecard" we can pull up on the CDU after each landing that will show us various parameters such as max and average descent rate, average N1, max deviation above/below glideslope and a bunch of other stuff.  The parameter I pay the most attention to as I think it gives the best overall assessment of the approach and landing is the seconds from 50' AGL to touchdown.  7-10 seconds is what our check airmen like to see.  Longer and you floated too much, shorter and you didn't flare enough.

 

That's pretty cool, and actually makes a lot of sense.

[Spin737 102]

Oh slaabs...Dowtys or Hamstands.

Drop the Dunlops and drag the Dowtys! Ie. Gear down, condition levers Max.

[scandinavian13 5,192]

Drop the Dunlops and drag the Dowtys! Ie. Gear down, condition levers Max.

 

haha - and this is exactly why I asked. Nice!