Approach Design Question

[Graueradler]

Runway has medium intensity runway lighting, no approach lighting, and a WAAS-LPV approach with minimums of 275 feet and a mile. Would the addition of ODALS approach lighting allow the minimums to be reduced. The outermost ODALS light would be 1500 feet closer to the point at which the glide slope reaches decision height. It seems like the minimum vis could be reduced from 1 mile to 3/4 mile. (Russellville, AR RWY-7)

 

[RussR]

I'll have to verify this, maybe tomorrow, but if I recall correctly, ODALS do not get light credit, meaning there is no reduction in minimums.

 

[Graueradler]

I was told yesterday that the Airport Improvement Program manual says that if ODALS aren't required to improve minimums, then they aren't eligible for a grant. We've had them on our Capital Improvement Plan for about 3 years on the basis that even if they don't improve minimums, the ability of the pilot to see the runway environment at decision height is significantly improved.

 

[SCCutler]

I love GPS approaches, especially the LPV ones, but the absence of approach lighting systems is the thing that worries me the most - in cruddy conditions, it can be remarkably difficult to spot the runway environment.

I'd expect an ODALS to be a real improvement, and worthwhile regardless of whether its installation allowed a lower approach flight vis or not.

 

[RussR]

I stand corrected. As promised, I looked it up. This was changed just in the last couple of years, but ODALS now qualify for a reduction.

From 8260.3B, Table 3-2, ODALS are categorized as a "Basic Approach Lighting System" (BALS).

From Table 3-5a, with a HAT of 275ft, with a BALS, the approach can be authorized down to RVR 4000 or 3/4 sm vis.

I would contact your regional flight procedures office to verify.

http://www.faa.gov/air_traffic/flig...dures/ifp_initiation/ifp_development_offices/

 

[somorris]

I believe the ODALS could get you down to 3/4 mile. However, it may make more sense to try to get a MALSR or similar. You can get lower, and the cost differential may not be that significant, considering the federal support available. The MALSR, in my opinion, is far superior in low visibility.

 

[Ted]

More lighting is more better. I agree with Spike that poor lighting is a problem that GPS approaches see. I remember shooting the GPS approach semi-iced up into Estherville getting to Tony and Leah's wedding in the crud and not seeing the runway when I broke out. Found it, but took a minute.

Having WAAS is also very nice.

 

[RussR]

To expand on what somorris states, a MALSR would definitely be an improvement over ODALS (and could get you 1/2 sm vis). From the above mentioned Table 3-2, MALSR, ALSF-1/2, and SSALR are all considered the "best" approach lighting systems (Full ALS) and get the lowest minimums. But there is an Intermediate ALS category which includes MALSF's, and this category still only gets you 3/4 sm, so no minimums benefit over an ODALS.

Also, to get less than 3/4 sm vis requires precision runway markings (8260.3B, para 3.1.3). Russellville currently has non-precision markings, which works down to 3/4 mile but not below. So even if you got MALSRs there, it'd be stuck at 3/4 mile until repainting.

There are likely other considerations as well. Good luck!