Wet Footprint?
12-29-2008 | 11:43 AM
#2
Prime Minister/Moderator
Joined: Jan 2006
Posts: 44,618
Likes: 557
From: Engines Turn or People Swim
If you lost all engine(s), it would be the max glide distance which would still result in a water landing. So it depends on geography...
If you are over the open ocean, it would be the airplane's max glide distance.
If you are near enough to make it to dry land, it would be the distance to land.
If you are over the open ocean, it would be the airplane's max glide distance.
If you are near enough to make it to dry land, it would be the distance to land.
12-29-2008 | 12:23 PM
#3
Gets Weekends Off
Joined: Jul 2008
Posts: 370
Likes: 0
From: G550 & CL300 PIC
There are a few scenarios.
Take PHNL-KLAX.
At your mid point you lose cabin pressure and have to descend to 10,000 feet, you then divert to the nearest suitable airport, can you make it back to land? If you can't then you have a wet footprint because you going swimming.
You can consider an all engine divert, all engine depressurized divert, or a single engine divert. All starting from the worse possible locations given planned wind, altitude, weight and temperature.
Take PHNL-KLAX.
At your mid point you lose cabin pressure and have to descend to 10,000 feet, you then divert to the nearest suitable airport, can you make it back to land? If you can't then you have a wet footprint because you going swimming.
You can consider an all engine divert, all engine depressurized divert, or a single engine divert. All starting from the worse possible locations given planned wind, altitude, weight and temperature.
01-14-2009 | 09:00 PM
#6
Gets Weekends Off
Joined: Jan 2008
Posts: 323
Likes: 0
From: A320
This is the reason we have ETPs (Equal Time Points) that assure we can be within 1hr of a suitable alternate airport at anytime during a deep water flight. They are calculated by dispatch and entered into the boxes before and updated during flight. They assume 10k feet for winds & fuel burn.
01-22-2009 | 07:58 AM
#7
On Reserve
Joined: Jan 2009
Posts: 19
Likes: 0
From: Business Owner
Here's how I understand it. Used to fly Westwinds and Hawkers. Our validation flight for 135 cert had this scenario. MRY-HII(don't know Identifier for Hawaii).
If it was a 2100nm leg, the westwind/hawker 700 had a 700 mile wet footprint. If anytime during the middle 700 miles we lost an engine, lost pressurization or the gear had drooped, we would be landing in the water. Any of these things would cause us to drop altitude or create more drag, thus decreasing the range.
Not a pleasant thought. Obviously, for the purpose of 135 cert, this was a no go.
Equal Time Point and Point of No Return are interesting planning as well.
If it was a 2100nm leg, the westwind/hawker 700 had a 700 mile wet footprint. If anytime during the middle 700 miles we lost an engine, lost pressurization or the gear had drooped, we would be landing in the water. Any of these things would cause us to drop altitude or create more drag, thus decreasing the range.
Not a pleasant thought. Obviously, for the purpose of 135 cert, this was a no go.
Equal Time Point and Point of No Return are interesting planning as well.
01-27-2009 | 09:04 PM
#8
Gets Weekends Off
Joined: Feb 2007
Posts: 393
Likes: 0
From: Left
Here's how I understand it. Used to fly Westwinds and Hawkers. Our validation flight for 135 cert had this scenario. MRY-HII(don't know Identifier for Hawaii).
If it was a 2100nm leg, the westwind/hawker 700 had a 700 mile wet footprint. If anytime during the middle 700 miles we lost an engine, lost pressurization or the gear had drooped, we would be landing in the water. Any of these things would cause us to drop altitude or create more drag, thus decreasing the range.
Not a pleasant thought. Obviously, for the purpose of 135 cert, this was a no go.
Equal Time Point and Point of No Return are interesting planning as well.
If it was a 2100nm leg, the westwind/hawker 700 had a 700 mile wet footprint. If anytime during the middle 700 miles we lost an engine, lost pressurization or the gear had drooped, we would be landing in the water. Any of these things would cause us to drop altitude or create more drag, thus decreasing the range.
Not a pleasant thought. Obviously, for the purpose of 135 cert, this was a no go.
Equal Time Point and Point of No Return are interesting planning as well.
01-27-2009 | 09:18 PM
#9
On Reserve
Joined: Jan 2009
Posts: 19
Likes: 0
From: Business Owner
No, we never did the trip. It was a planning exercise for 135 ops for our POI. And a correction, if we dropped altitude, it wasn't the drag that created the problem, it was the fuel consumption at the lower altitudes.
01-27-2009 | 09:23 PM
#10
Gets Weekends Off
Joined: Feb 2007
Posts: 393
Likes: 0
From: Left
Thats good to hear. A wet footprint is a big time no go deal for most. Some aircraft were just never designed to be flown in extended range overwater operations.
My boss wanted us to take the Lear 55 to Hawaii. Until we gave him the breakdown on the fact that he would have to have a boat meet us to take him the last 500 miles.
My boss wanted us to take the Lear 55 to Hawaii. Until we gave him the breakdown on the fact that he would have to have a boat meet us to take him the last 500 miles.
