Flying Across Bass Strait to Tasmania!

[farri]

Due to the engine failure and ditching of the Thruster into Bass Strait, I`ve put together some figures to show the various glide ratios required to reach land. The objective is to create awareness of the safety of the flight.

 

For the purpose of the exercise, I`ve used Google Earth and I`ve taken the shortest possible distance, from the mainland to Tasmania, via King Island . I`ve only taken the legs over water, not taking into account the suitablity of any land as a safe landing area, nor have I factored in any wind speed. To simplify the exercise, I`ve left out the decimal points of the distances in feet.

 

Leg 1.....Mainland to king Island, Distance, 48.83 nm = 296,696 feet. Halfway point, 24.41 nm = 148,317 feet.

 

Leaving the mainland with an altitude of 10,000 feet amsl, the glide ratio required to reach King Island is 29.6:1........Glide ratio from the halfway point is 14.8:1.

 

Leg 2: King Island to Cape Grim, Tasmania, distance, 48.38 nm = 293,962 feet. Half way point, 24.19 nm = 146,981 feet. Leaving King Island at 10,000 feet amsl, glide ratio to Cape Grim is 29.3:1. Glide ratio from the halfway point is 14.6:1.

 

Let`s assume the crossing is being done in a WB Drifter which has a glide ratio of 8:1... Flying at 10,ooo amsl, if the engine fails at the halfway point from the mainland to King Island, the aircraft will travel a horizontal distance of 80,000 feet or 13.16 nm. It will fall short of King Island by 11.24nm = 68,317 feet.

 

Frank.

 

Ps, With different scenarios the figures will change but please correct me if my figures are incorrect.

 

 

[Ultralights]

how about doing the same calculations going down the Flinders Island side, there is a lot more land between Mainland, at Wilsons Prom, and the coast in the top north east corner of tassie. King Island is the only land on the western side of the straight, but the path via Flinders is doted with Islands. so the distance to "land" is far less than 40 Nm.

 

 

[fly_tornado]

don't you want to find land with at least 1000 feet so you can choose your landing spot?

 

 

[Dafydd Llewellyn]

Well, I'm hoping for a glide ratio of around 24:1 in the motorised Blanik . . .

 

 

[farri]

For the purpose of the exercise, I`ve used Google Earth and I`ve taken the shortest possible distance, from the mainland to Tasmania, via King .

Frank.

 

 

[kaz3g]

Then there is the almost inevitable SW blowing...

 

Kaz

 

 

[rankamateur]

don't you want to find land with at least 1000 feet so you can choose your landing spot?

The pilots in previous ditchings may have just been happy to have somewhere to swim ashore and sit with the seals.

 

 

[facthunter]

Sharks swim with seals too. Farri has thrown us a few figures to consider and you are not going from aerodrome to aerodrome. Rock fishermen are on land when they get washed off the rocks. Most of them drown a few yards from the shore because you can't safely get out of rough water onto rocks. There was a time when Bass Strait was known as Australia's Bermuda Triangle. Wasn't it stated that this was the first survived ditching . Nev

 

 

[Ultralights]

i remember a while ago there was a ditching, pilot survived, was spotted by rescue aircraft, but bureaucracy got in the way over who's jurisdiction the rescue fell to, and sadly the pilot floated away never to be seen again.

 

 

[farri]

how about doing the same calculations going down the Flinders Island side.

Calculations are taken from 10,000 amsl.

 

Leg 1: Wilsons Promontory to Rodondo Island 5.7 nm = 34633`, glide ratio required 6.4:1, glide distance, 10.53 nm = 64,000`

 

Leg 2: Rodondo Island to Curtis Island 19 nm = 115446` glide ratio required 11.5:1, glide distance, 18.92 nm = 115,000`

 

Leg 3: Curtus Island to Deal Island 31.3 nm = 190182` glide ratio required 19:1, glide distance, 31.26 nm = 190,000`

 

Leg 4: Deal Island to Craggy Island 20 nm = 121522` glide ratio required 12.15:1, glide distance, 19.99 nm = 121,500`

 

Leg 4: Craggy Island to Flinders Island 9.3 nm = 56507` glide ratio required 5.6:1, glide distance, 9.21 nm = 56,000`

 

Leg 5: Clark Island to Tasmania 12 nm = 72913` glide ratio required 7.2:1, glide distance, 11.84 nm = 72,000`

 

In part, my point is! How many pilots of recrational aircraft bother to calculate gliding distance. Keep in mind that these figures require that the altitude remain at 10,000 feet. I havn`t factored in wind speed and direction as this is relative to the flight at the time.

 

Frank.

 

Ps, If my figures are wrong, please correct me.

 

 

[Dafydd Llewellyn]

There's a glide range option in Oz Runways; however any such indication relies on an assumed wind. Glider computers estimate the wind from the drift whilst the glider is circling in the previous thermal; but that will not give the wind at lower levels. I don't know how OzRunways gets its wind. The L:D figures for glide in the FM show the best glide angle relative to the air; if the air is moving, the distance made good over the ground can radically alter the distance made good. For example, if your aircraft has a best glide angle of 12:1 at 60 knots, and you're gliding into a 30 knot headwind, the effective angle relative to the ground will be 6:1. You'd want to increase your glide speed in such a situation - but the necessary data to calculate how much is not supplied in the normal style of FM. A 90 degree crosswind costs distance, too; the wind has to be aft of abeam before it starts to be favourable. Also, as somebody pointed out, you need to arrive over your target with sufficient height in hand for a circuit of some sort; also "glide range" displays do not always take account of intervening terrain.

 

The presence of wind shifts your "point of no return" from the mid-point of the leg, also; so calculating how high you need to be at each stage, to glide out of trouble, is not simple.

 

 

[Alan Cameron]

First try to get your drifter to 10,000 ft???

 

From the reports on TV I gather that no life raft was carried, would that not have been a mandatory item for a longish over water crossing?

 

 

[farri]

My figures are just that! figures! an example of the glide ratios and glide distances of those legs.

 

I havn`t said that any of those Islands are suitable for a safe landing! They may not be! Something that needs to be considered when flight planing.

 

Frank.

 

 

[Marty_d]

Spirit of Tasmania cruises at 27 knots. If you fly a zig-zag pattern over (and slightly ahead of) it, then you've got a guaranteed pick up if you ditch. And it's got a fully stocked bar to assist recovery.

 

Just sayin!

 

 

[farri]

Marty, I love it!

 

Frank.

 

 

[ahlocks]

Marty's on a roll tonight.

 

 

[Marty_d]

Aw shucks

 

 

[turboplanner]

Better still, put your Thruster on the boat - it'll cost less

 

 

[biggles]

Good luck with Rodondo Is. !

 

Bob

 

http://cehorn.customer.netspace.net.au/rodondo.htm

 

 

[metalman]

Calculations are taken from 10,000 amsl.Leg 1: Wilsons Promontory to Rodondo Island 5.7 nm = 34633`, glide ratio required 6.4:1, glide distance, 10.53 nm = 64,000`

 

Leg 2: Rodondo Island to Curtis Island 19 nm = 115446` glide ratio required 11.5:1, glide distance, 18.92 nm = 115,000`

 

Leg 3: Curtus Island to Deal Island 31.3 nm = 190182` glide ratio required 19:1, glide distance, 31.26 nm = 190,000`

 

Leg 4: Deal Island to Craggy Island 20 nm = 121522` glide ratio required 12.15:1, glide distance, 19.99 nm = 121,500`

 

Leg 4: Craggy Island to Flinders Island 9.3 nm = 56507` glide ratio required 5.6:1, glide distance, 9.21 nm = 56,000`

 

Leg 5: Clark Island to Tasmania 12 nm = 72913` glide ratio required 7.2:1, glide distance, 11.84 nm = 72,000`

 

In part, my point is! How many pilots of recrational aircraft bother to calculate gliding distance. Keep in mind that these figures require that the altitude remain at 10,000 feet. I havn`t factored in wind speed and direction as this is relative to the flight at the time.

 

Frank.

 

Ps, If my figures are wrong, please correct me.

as far as reducing risk this is the better route, still has the pucker factor but a lot better than the other way

matty

 

 

[facthunter]

You could work points of no return for each sector using forecast winds. The easiest way would be is to use the sink rate at best glide to give time and the relevant groundspeed to each portion of land. Work from the land backwards to get your descent point. In situations where there is a significant head/tail wind, you must vary your chosen glide speed to get best range, making the whole thing quite complex, as the sink rate will alter. What the whole exercise will show is that for some parts of the trip you CAN reach land, and for quite a lot of it you can't. If a 180 degree turn is needed, that will lose precious height too, and you may have to manoeuver at destination, which may only be a lump of rock, but you might want to pick one side of it with protection. Nev

 

 

[farri]

Good luck with Rodondo Is. ! Bob http://cehorn.customer.netspace.net.au/rodondo.htm

G`Day Bob, , You`ve been lying low for a while! Hope you and Sal all good!

 

You`ve helped make part of my point! How many of those little Islands would be a safe place to land? Just because there`s a bit of land to put down on, doesn`t follow that you will walk away.

 

My King Island example was due to the fact that I`ve read a few times of guys saying that King Island is a way to go. On the other thread about the Thruster and Banks Strait, I read of guys in Drifters flying across Bass Straight. More guts than me! As for survival gear, that`s all good and well for meeting the regulations but it doesn`t guarantee survival!!!

 

At times I fly over the local off shore Islands, but I only do so at low tide so that there is plenty of beach on the mainland to land on and then always at an altitude that I can safely glide back! at times, right back to my strip. Wouldn`t do it any other way.

 

Frank.

 

 

[farri]

Nev, I reckon the two guys in the Thruster that went down, wouldn`t have had the knowledge to do what you have sugested in your post #21. That`s for experienced pilots who know their stuff.

 

To me! the proof is in the amount of fatal`s that keep occuring.

 

Frank.

 

 

[facthunter]

You are right franco. I tried to get the principle into it. If a few examples are worked through it becomes easy. Your theory makes the most sense. I've never done Bass Strait in a single engined machine, and doubt I will. Nev

 

 

[biggles]

G`Day Bob, , You`ve been lying low for a while! Hope you and Sal all good!

 

Yeah Frank all good here . Will email you soon

 

Bob