AirWillie6475
Topic Author
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Alternate Departure Airport

Sat Mar 04, 2006 7:39 am

For you airline pilots out there, is there such thing as a alternate departure airport? If there is, why is there a need for an alternate airport?
 
CosmicCruiser
Posts: 2049
Joined: Tue Feb 22, 2005 3:01 am

RE: Alternate Departure Airport

Sat Mar 04, 2006 7:50 am

In some cases you can dept with lower minimums than you can land with therefore you have an alt that you can go to in the event of an emerg. after dept.
 
jspitfire
Posts: 284
Joined: Fri Feb 18, 2005 2:50 pm

RE: Alternate Departure Airport

Sat Mar 04, 2006 8:49 am

I just learned about this in groundschool. For most departures, the minimum visibility is 1/2 SM, and there is no minimum ceiling. So, this means that if the weather is really bad, you can likely depart, but you probably won't be able to get back in.

If I remember correctly, the alternate has to be within 60 minutes flight time at the aircraft's single-engine cruise speed. If the aircraft is certified for ETOPS, then I think it goes up to 120 minutes. I should know this, considering I had a test on it today, but if I'm wrong, please correct me.

Jason
 
Goldenshield
Posts: 5008
Joined: Sun Jan 14, 2001 3:45 pm

RE: Alternate Departure Airport

Sat Mar 04, 2006 9:11 am

I can only speak for U.S. regulations.

First, the regulations in question:

§ 91.1039:

(d) No person may take off an aircraft under IFR from an airport where weather conditions are at or above takeoff minimums but are below authorized IFR landing minimums unless there is an alternate airport within one hour's flying time (at normal cruising speed, in still air) of the airport of departure.

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§ 135.217 IFR: Takeoff limitations.
No person may takeoff an aircraft under IFR from an airport where weather conditions are at or above takeoff minimums but are below authorized IFR landing minimums unless there is an alternate airport within 1 hour's flying time (at normal cruising speed, in still air) of the airport of departure.

------------------

§ 121.617 Alternate airport for departure.
(a) If the weather conditions at the airport of takeoff are below the landing minimums in the certificate holder's operations specifications for that airport, no person may dispatch or release an aircraft from that airport unless the dispatch or flight release specifies an alternate airport located within the following distances from the airport of takeoff:

(1) Aircraft having two engines. Not more than one hour from the departure airport at normal cruising speed in still air with one engine inoperative.

(2) Aircraft having three or more engines. Not more than two hours from the departure airport at normal cruising speed in still air with one engine inoperative.

(b) For the purpose of paragraph (a) of this section, the alternate airport weather conditions must meet the requirements of the certificate holder's operations specifications.

----

Part 91 requires a takeoff alternate within 1 hour's flight if the departure airport is below minimums, but it does not specify what kind of airport,or wether that airport should be forecast above landing minimums at the arrival time.

Part 135 reads the same as 91. While both 91 and 135 mention minimums required to list an arrival alternate, that rule is not extended to the takeoff.

Part 121, however, is a whole different ball game. Firstly, number of engines on the aircraft fall into play, requiring a maximum 1/2 hour for twins, and 1 hour for those with 3 or more engines. Secondly, the regulation states that the weather conditions (forecast) at the alternate must be above alternate landing minimums, as required by 121, or as allowed in that carrier's OpSpecs.
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cylw
Posts: 408
Joined: Sun Apr 09, 2000 2:34 pm

RE: Alternate Departure Airport

Sat Mar 04, 2006 3:36 pm

Quote:
Part 121, however, is a whole different ball game. Firstly, number of engines on the aircraft fall into play, requiring a maximum 1/2 hour for twins, and 1 hour for those with 3 or more engines. Secondly, the regulation states that the weather conditions (forecast) at the alternate must be above alternate landing minimums, as required by 121, or as allowed in that carrier's OpSpecs

For twins, isn't it 1 hour at the one engine speed??
 
OPNLguy
Posts: 11191
Joined: Tue Jun 15, 1999 11:29 am

RE: Alternate Departure Airport

Sat Mar 04, 2006 4:09 pm

Quoting Goldenshield (Reply 3):
Part 121, however, is a whole different ball game. Firstly, number of engines on the aircraft fall into play, requiring a maximum 1/2 hour for twins, and 1 hour for those with 3 or more engines.

That's one hour for twins; two hours for 3- or 4-engined birds...

(1) Aircraft having two engines. Not more than one hour from the departure airport at normal cruising speed in still air with one engine inoperative.

(2) Aircraft having three or more engines. Not more than two hours from the departure airport at normal cruising speed in still air with one engine inoperative.

Back to recurrent!  Wink
ALL views, opinions expressed are mine ONLY and are NOT representative of those shared by Southwest Airlines Co.
 
Goldenshield
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Joined: Sun Jan 14, 2001 3:45 pm

RE: Alternate Departure Airport

Sat Mar 04, 2006 9:34 pm

Oops. My bad. I had just pasted the regulation, too.  Wink

I have no idea what I was thinking there. Perhaps I should stop posting when I'm 1/2 asleep.  Wink
Two all beef patties, special sauce, lettuce, cheese, pickles, onions on a sesame seed bun.
 
OPNLguy
Posts: 11191
Joined: Tue Jun 15, 1999 11:29 am

RE: Alternate Departure Airport

Sat Mar 04, 2006 11:25 pm

Quoting Goldenshield (Reply 6):
I have no idea what I was thinking there. Perhaps I should stop posting when I'm 1/2 asleep.

Nah, it's just CVL (cranial vapor lock)--it happens to everyone at one point or another..  Wink
ALL views, opinions expressed are mine ONLY and are NOT representative of those shared by Southwest Airlines Co.

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