Minimum TAS for east coast >> west coast to avoid bad weather ?

[RFguy]

What are people's opinions for the minimum TAS required to fly from east coast to west coast and not encounter 'the next weather system' and subsequent likely day on the ground, perhaps.

?

(going east is fairly easy) 

IE take off from east coast just after bad weather passes. If you stay stationary, you probably have 3 to 5 days before the 'next one' arrives. but flying west, that changes things. 

[Thruster88]

As a farmer who watches weather especially leading up to harvest, it varies quite a bit. Right now you could go in a Thruster no worries, decent tail wind to boot.  If in doubt Glasair III my friend.

 

[Carbon Canary]

Transit of weather systems across the Earths surface is influenced by the Earths rotation.

At the Equator the rotation speed is around 1,600kmh.

You may need to turbocharge the Jab.

[RFguy]

I will rephrase that to :

WHAT IS THE MINIMUM GROUND SPEED......

If the weather  system  at 33 deg have a  period is 72 hours. and the distance is 3200 km.

then I think , assuming neutral wind, you have a 72 hour window, or an avg speed of 44 kmh.

and if you fly 6 hours per day, multiply that number by 6 = 266kmh. (144kts TAS).

somewhere  there would be the average wind speed across the path opposing your progress  call it  40kmh, so now your TAS needs to be 166 kts.

Thruster88 indeed these current weather conditions are unusual.

The Lancair is needed  (no, I am not going to buy a Lancair) . The RV6A will just do it.... 

I'm not about to start doing this, but I have a friend who flys a Tecnam 2004 from Canberra to Kalgoolie and he's found that getting a long enough weather window in that plane (TAS120) is difficult as a lone pilot.

 

Increase the flying hours to 8 per day, and utilize two pilots, required TAS is down to 124kts .
Problem with that and VFR , that that with stops is probably going to run out of light half the year.

 

 

 

 

 

Edited December 17, 2022 by RFguy

[Bosi72]

Assuming the goal is to get to Perth in one day, flying at power/altitude/weight which produces the highest TAS will get you there sooner, but it may put stress on the engine.

 

Don't know which aircrafts you are flying, but some POH's have "Power-Density Altitude-TAS", and "Power-Fuel Flow" charts. Bob Taits CPL Performance book provide some answers how to resolve these problems.

 

Also allow time for refuelling, rest, etc..

 

Many people do it in two stages staying overnight in Forrest.

 

The best way is to enter the route details into EFB, then analyse the results.  Below is the extreme case scenario without stops, direct lines. Perth EOD today is 11:48UTC, subtract 10mins for landing time, and also departing early morning at BOD will give you another ~5 hours.

 

 

[RFguy]

Hi Bosi. ahhh no.......maybe re read the post before your post.

A good pilot shouuldnt need an EFB tool to figure this out. This is basic calcs and a little judgement.

 

[facthunter]

Ground speed is the most relevant. Some low TAS planes you don't fly if the headwind component is too high Even at 200 Kts it takes forever to get to Perth.  Nev

[RFguy]

well, puttign aside the odd wx lately, per my post :
 

and I seem to have screwed up the previous calcs, re-doing : 
Given that if you leave the east coast  just on the back of the previous bad weather, the next front will be crossing Perth

1737nm, 72 hour (3 day) period  between weather fronts.

but the next front is crossing the destination  at the time you are leaving

So it is inevitable that you will hit the  weather change. You cant avoid it, so one must plan an off day. 

solving for time for intercept given Vx  (weather=24 kts) and Vy( plane =  125kTAS)
t = d/(Vy+Vx)  = 11.56hours to intercept - this assumes continuous flying. but you are not doing this. 

So I'll re do this later to account for hours per day flown.

In fact, I will write an online tool for this.
 

Edited December 18, 2022 by RFguy

[Bosi72]

37 minutes ago, RFguy said:

...maybe re read the post before your post...

A good pilot shouuldnt need an EFB tool to figure this out. This is basic calcs and a little judgement.

 

I did read both of your posts 3 times and still couldn't understand what was asked.

 

>assuming neutral wind, you have a 72

>hour window, or an avg speed of 44 kmh.

 

is neutral wind 0kmh or 44kmh?

 

>and if you fly 6 hours per day, multiply >that number by 6 = 266kmh. (144kts TAS).

 

I don't understand this calculation? does this mean if you fly 10 hours a day that number would be 440kmh (237 kts).

 

If my post above isn't helping, please disregard.

 

 

 

 

[facthunter]

The weather patterns vary a lot to just use averages for the "windows". With a little Plane (bugsmasher) fly for fun and be prepared to wait out unsatisfactory weather. Human factor s 101.  People who fly for a living don't have that option. They fly in bad weather and carry holding or alternate fuel  Nev

[RFguy]

Bosi, see above - I screwed up my initial calcs

[RFguy]

well, puttign aside the odd wx lately, per my post :
 

and I seem to have screwed up the previous calcs, re-doing : 
Given that if you leave the east coast  just on the back of the previous bad weather, the next front will be crossing Perth

1737nm, 72 hour (3 day) period  between weather fronts.

but the next front is crossing the destination  at the time you are leaving

So it is inevitable that you will hit the  weather change. You cant avoid it, so one must plan an off day. 

solving for time for intercept given Vx  (weather=24 kts) and Vy( plane =  125kTAS)
t = d/(Vy+Vx)  = 11.56hours to intercept - this assumes continuous flying. but you are not doing this. 

So I'll re do this later to account for hours per day flown.

In fact, I will write an online tool for this. hmm is it just the average  airplane speed to account for stopped time ?
ahh screwed it up again

if 125TAS, - 24kts wind.  average per hour is (125-24 . 6 )=606 / 24 = 25.25kts
Then time to intercept is : 35 hours into the trip, or late on the 2nd day if you start 1st day early. 

 

Edited December 18, 2022 by RFguy

[facthunter]

React to the situation that presents itself as the flight progresses. That's airmanship.  You can usually outrun weather systems, if you turn around. Crosswind limits require alternates  if they are above what is safe for you and your plane.  If the weather is bad enough, your plane's safety on the ground even may be threatened.  Nev

[RFguy]

So this Goulburn- Kalgoolie roughie

to go from Goulburn to Kalgoolie, at 120TAS (tecnam)with 24 kts headwind)   and fly 6 hours per day . Vavg = 24 kts

1500nm .and  24kt westerly. time to intercept weather = 31 hours.
 

late in the 2nd day. so you almost  get two days, then a day maybe on the ground
in two days you make 1152nm, out of the 1500nm, so the 3rd day is a rest and the 4th day is a short 348nm.

 

and Nev, as you say, plan around  alternates,  especially with  airfields that do thave crosswind  options. 

NUMEROUS plans need to be run  to figure out alternate groups per day..

and then, likely updating daily. 

 

Edited December 18, 2022 by RFguy

[RFguy]

Given that if you fly for 8 hours instead of 6 hours on the first day, that puts wx intercept at 27 hours (tecnam)  you'll probably run into the weather a couple hours after sunrise on the 2nd day.  which is not good.
so you could fly long the first day and plan a rest day for 2nd .  flying 8 hours on the first day gets you 768 out of 1500nm means 732 nm on 3rd day. 
so 8h + rest + 8h . OR...  6h + 6h + rest + 4h

either way- yes, re evaluate FULL plan daily. 

[facthunter]

Do you have a reliable estimate of the rate the systems move eastwards? It's usually ESE actually but no two systems are identical.  Your GROUND speed is the only control /measure of distance covered in a specific time.. Most "Howgozit's" rely on Ground Nautical Miles per fuel units used.  Forecasts of winds can be a long way out at times.  My worst experiences of that are across the Nullarbour and ground level winds affected by high Land temps adjacent to the ocean  are often  strong.   Nev

[RFguy]

Hi Nev
reliable estimate?  - not really.that would have to come during the daily planning. 

But doing some numbers like this helps one when doing some mental calcs weed out calc errors from maybes.

 

The other thing. distance attempted per day would have to provide for runways with crosswind alternates, so likely to be a longer track.  I'd be looking for stops with Cross available. But that might not be easy to find. some local knowledge would assist....

You are hardly goign to want to go looking for an alternate late in the day- some I presume some pilots rather than try for their alternate, will try a crosswind landing that might be beyond their fatigue-skill level late in the day. 

 

[tillmanr]

Maybe I missed something. If your aircraft is flying at 120 knots into a headwind of 24 knots your ground cover is 96 n miles per hour.

Dividing your travel distance1550 by this speed to determine the flying time required, 15.6 hours.

A simplistic approach I accept.

Edited December 18, 2022 by tillmanr
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[facthunter]

Going  west, you are going towards a system that is approaching you. That rate of closure could be quite time deficient. On the Sydney Perth run you could encounter two systems on RPT.  Near the east coast the air mass could contain much more moisture as it may come from north of the Broome area with plenty of Tropical Maritime air . 

[onetrack]

A lot of flyers have come to grief flying Westwards into approaching adverse weather events. You're effectively tripling or quadrupling the speed of approaching weather.

 

Even the BOM is cautious about the accuracy of their forecasting more than 3 days out. Weather events are often quite unpredictable, and adverse weather can develop rapidly, particularly over the interior in Summer.

 

High and low pressure systems can develop quickly, and move S and N as well as W to E. One local unusual pattern that has been developing lately, is low pressure systems forming off the W.A. coast far higher than normal for this time of year.

They are forming NW of Geraldton and travelling through the pastoral regions and interior of W.A. in a SE'ly direction, into the Bight. It is a quite uncommon weather pattern for this time of year.

 

However, these low pressure systems have not been bringing large amounts of rain, just cloudy conditions with light rainfall.

[facthunter]

Big difference  between summer and winter  troughs and weather systems. Summer is going to be rough air on the hot days up to higher levels as the day progresses at typical unpressurised flight cruise levels. This is tiring and unpleasant..on a long flight. Nev

[poteroo]

Have been traversing the Nullarbor since 1971, in everything from a Jabiru 120 to a Beech Baron 55. It hasn't become any shorter, nor the winds really any different. You do need to heed a few common sense rules-of-thumb though:

 

1. Always use GS, because your TAS will vary lots with altitude and power settings.

2. Going East - generally fly as high as you can, and only add 10kts to rough planning

3. Going West - generally fly below 2000 ft to avoid the ever present W/NW, take 20/25 kts off your TAS

4. In winter, keep inland as much as you are able

5. In summer, follow the coast to pickup any onshore breezes, and it's cooler

6. Plan on maximum 8 hrs flight in any one day - see 12.

7. Stay overnight where there is good shelter available for the aircraft, eg, Pirie, Nullarbor, Forrest, Border Village, Caiguna, Balladonia and Myrup (ESP). Ceduna, Esperance and Hopetoun are very exposed.

8. Call ahead to check fuel availability status, ie, both AVGAS and PULP 95/98

9. The weather systems almost always lie NW/SE. They usually  move at 20-30 kts. Going W, the wx always seems to be faster than you planned. It fills the sky alarmingly fast.

10. Summer systems are trough lines which are small TS, with lots of lightning, not much rain, but sharp NE/NW/W winds - keep your eye on the ground for dust disturbance and slow down to <Va when cutting through the trough line, but always on the NW side of any TS or cell.

11. In winter, divert inland so that the cold front will be narrower,  keep heading NW until you can see well ahead.  You have diversion options always on that side.

12. appropos the flying time per day - you must plan for the worst case scenario in that you could easily need to divert late in the day when you hoped for destination has a screaming crosswind with blowing dust. Aim to get to your destination min 2 hrs before last light while holding an alternate plan for 1 hrs flight time.

13. carry water + food + warm clothes with you - cringing o/n under a line of mallee on a remote station strip is always more bearable if you are not thirsty, hungry or freezing. The Nullarbor coast, but really everywhere from Ceduna to Albany, is subject to very strong seabreezes in summer, and the temps fall well into the 10-15 range...despite a day temp of 30-40. 

14. Make sure that you have any and every station and mining strip co-ords in your GPS.

 

Remember the old adage - 'much better to be safely sitting down here, than being up there and wishing you were not. 

 

 

Happy NY...cheers,

 

 

 

 

 

[rgmwa]

Great advice. I’ve made the crossing three times and many others here will have done it more often I’m sure. It’s fascinating country to fly over but you need to do your homework when it comes to weather (when in doubt, wait it out), fuel, safe places to land, aircraft condition and having the right gear with you.