A Fuel Load That Doesn't Add Up on a Marginal Denver Arrival

Alternate required. Under the domestic alternate rule (14 CFR 121.619), an alternate is required whenever the destination forecast, from 1 hour before to 1 hour after the ETA, is below a 2,000-foot ceiling or 3 SM visibility. ETA 2130Z gives a window of 2030Z-2230Z. The TEMPO group of 1/2 SM and VV002 sits entirely inside that window, and a TEMPO is part of the forecast - a probable improvement later does not remove the requirement.

Alternate must be checked against 121.625. For an airport with a precision approach, the alternate forecast must show at least a 600-foot ceiling and 2 SM visibility at the ETA. KCOS at 700 OVC and 3 SM with an ILS clears that with margin, so KCOS is a legal alternate for this arrival.

Two things worth flagging in the release: the alternate must be reachable from the MEA without descending below minimum enroute altitude until the approach segment, and the alternate check uses the forecast at the time the flight would actually arrive at the alternate, not at the destination ETA.

With an alternate required, the minimum is: taxi out + trip + alternate + 45 minutes at normal cruise.

• Taxi out: 300 lb
• Trip: 5,400 lb
• Alternate (KCOS): 1,400 lb
• 45-minute reserve: 3,400 x 0.75 = 2,550, planned as 2,600 lb
• Total: 9,700 lb

The release shows 9,400 lb. The 300 lb discrepancy is exactly the taxi fuel - the flight planner built the total from trip, reserve, and alternate only and left taxi fuel out of the brake-release figure. The flight is 300 lb short of the regulatory minimum before any judgment margin is considered.

That 300 lb is the floor, not the plan. The destination is forecast below 2,000-3 through the arrival window with a TEMPO of 1/2 SM, so a missed approach and a divert to KCOS is a realistic outcome rather than a remote one. A sensible release adds holding fuel for one approach and a second try (roughly 20 minutes at cruise burn, ~1,100 lb) on top of the legal minimum. Action: add fuel to at least 9,700 lb, ideally ~10,800 lb, or reduce payload to make room. Do not sign the release at 9,400 lb.

Operational control is exercised jointly by the dispatcher and the pilot in command (121.533). 'Take a look and hold' describes a tactic, not a compliance path: the release still has to carry legal alternate and fuel before the aircraft moves.

The specific problems with the captain's plan:

1. Holding at KDEN burns the fuel that is supposed to get the aircraft to KCOS. If the crew holds to minimum fuel and then diverts, they arrive at the alternate below the reserve - the fuel plan has been consumed by the hold.
2. The forecast is below 2,000-3 for the whole arrival window, so there is no basis for releasing without an alternate or for assuming the weather will lift on arrival.
3. The 300 lb taxi-fuel omission means the aircraft would launch short of minimum fuel even before the hold.

Dispatcher actions: hold the release, add fuel or offload payload, ensure KCOS appears on the release with its approach and forecast, and remark the release that a divert is likely. A cleaner option is a departure delay to put the arrival after 2230Z when the TEMPO expires - that removes the alternate pressure entirely and is cheaper than carrying the fuel.