ASA and flap 8 departures

[Russ]

Perhaps it just me, but it seems you guys do a lot of flaps 8 departures in the RJ. Spent a lot of time in DFW as of late. We (SkyWest) will be going out full doing flaps 20 with plenty of margin and see an ASA acft using 8. Is it my imagination? Who's your vendor for performance data? Not a slam, just curious.
Thanks

 

[180ToTheMarker]

According to the training dept the reason we do flaps 8 takeoffs on the longer runways is in case of an engine failure at V1. The RJ is easier to handle with only 8 degrees of flaps versus 20 in a low speed situation.

 

[AutoTransfer]

SOP

Our normal takeoff profile calls for flaps 8 departures unless runway length is an issue. Shorter runways and/or higher altitudes sometimes call for flaps 20. I have heard that most other operators use flaps 20 for most or all takeoffs. I don't really know why we always depart flaps 8. I believe single engine climb performance is enhanced when you use a flaps 8 profile and since we operate from a lot of 8000 ft + runways, why not use flaps 8.

AT

 

[rjcap]

Flaps 8 is used because of the following;

In case of a engine failure at V1, the aircraft will reach 1500 AGL and Vt sooner at flaps 8 then it would have at flaps 20.

Sooner in both instances of elapsed time from the engine failure and in terms of horizontal distance traveled along the ground.

 

[Russ]

OK, thanks for the 411
Do you guys see a lot of wake encounters as you get up farther down the runway out of busy places like DFW, etc?

 

[ILS8L]

climb performance

rjcap hit the nail on the head. Flaps 20 will get you off of the ground sooner (better for a short runway) but you will do better to 1500' with the flaps 8 profile.

 

[ifly4food]

OK, thanks for the 411
Do you guys see a lot of wake encounters as you get up farther down the runway out of busy places like DFW, etc?

Yes.

 

[Ty Webb]

With a long runway, your limiting factor is usually not runway length, but Second Segment climb requirements.

Second Segment starts after gear retraction, and requires a 2.4 degree climb gradient to the single-engine acceleration altitude (we use 800' AGL). If I remember correctly, 2.4 degrees equals 152'/nm climb.

In general, the lower flap setting gives better Second Segment climb performance.

If you use Stewart Manuals for your data, it will show you whether the limit is runway or second segment.

 

[SkyWestCRJPilot]

I was told by a checkairman at SkyWest that the reason why we use flaps 20 as normal is to reduce the likelihood of having a tire failure at high runway speeds that are encounted at flaps 8. I understand that this was especially a problem before the nose tire inflation had to be checked as part of the daily service check. The tire speeds for flaps 8 takeoffs are even higher at Salt Lake City due to the higher field elevation than for many other RJ operators that fly out of sea level airports. SkyWest had a main tire shred apart at V1 during the summer of '02 in PHX while doing a flaps 8 takeoff. The tread was ingested into one of the engines and the crew had to shut it down and return to land. High tire speed was a contributing factor in that incident. I guess each airline has to determine which risk to minimize, high tire speeds (for SkyWest often flying at higher field elevations) or weaker climb performance (ASAs preference).

 

[FmrFreightDog]

I was told by a checkairman at SkyWest that the reason why we use flaps 20 as normal is to reduce the likelihood of having a tire failure at high runway speeds that are encounted at flaps 8.

As I recall, max tire speed is 182 kts. I'd be surprised if that would be a factor when determining flap settings. Then again, I have actually had an instructor teach me a thing or two... On the other hand, I had one try to tell me that the flight director would follow the snowflake if you had the visual approach in the FMS, so.....