What did the flight plan say should be the flight time? As I posted in the thread in the 777 forum, I was 20 minutes behind the flight plan time (trip time) at 9 hours 9 minutes. 6 minutes was due to ATC delay at takeoff, and about 5 minutes was due to ATC at destination (vectors to final and much slower than planned). Not bad, considering.

 

Attached is the actual flight plan I flew.

 

Best regards,

Robin.

Robin

 

I don't remember what the flight plan was because there was no plan. The flight was a lark to see how the headwind component worked. Nothing as impressive as PFPX. I looked at the ETE on the PROG page but don't remember what it was. I believe with the FMS for the MD-11 you don't get an ETA until the plane is airborne.

 

Does Martinair fly between Atlanta and Vienna?

 

Michael Cubine

Officially, no. It's the route I flew for CTP.

 

I thought the ETA was presented after engine start? ETE before, with ETO appearing with required takeoff time if you set a time in the RTA page.

 

Best regards,

Robin.

Guys,

 

Don't forget that you're entering current winds for 6+ hour flights.  Currently, the weather programs we're using do not mix actual with forecast.  It's just all actual, taken using the current known winds.  The AWS also provides forecast winds, but from my understanding, these are not used by the weather programs for the sim.

 

Unless it's a very stable day, the winds will change, and your predictions based on the old winds will be off.  If you get one day where they're spot on, great.  If they're off the next day, then that's life.

 

 

 

If they were spot on all the time, the weather forecasters would also be spot on their forecasts every time.  We all know that's not the truth, so we all have to accept the truth that weather is weather, and it's not always predictable.

 

Zoom in closely enough on a computer monitor and all you'll see is red, green and blue.  It's only when you step back that you see a coherent image.  Don't get lost in the details trying to concentrate too much in the minutia.  There are reasons for having CONT fuel in the planning process.  Any difference between reported, forecast, and actual wind is one of them.

That's why I keep saying that wind entry into the FMS is largely a wasted effort. All that matters is the flight plan, and whether you hit the waypoints with the required fuel. The rest is down to chance.

 

Best regards,

Robin.

That's why I keep saying that wind entry into the FMS is largely a wasted effort.

 

I wouldn't call it a waste, but I wouldn't put as much faith in it as most do.

 

Too much black and white in the forums recently.  It's kinda bothering me.

To be honest I think that is representative of a larger problem in general; namely that people have stopped thinking for themselves because of all the rules/regulations saying what can or can not be done, and the fear put into people about digression from said rules, causing people to further stop thinking for themselves, even if those rules have been mis-interpreted by someone else and then mis-communicated for their own ends (plenty of real-world examples of this).

 

People are too afraid of questioning/challenging authority at the end of the day. Just because a rule or regulation says something, does not mean that you can't use your own discretion in applying it.

 

To put it another way - show me one incident/accident that occurred because someone failed to enter the winds into the FMS. Good luck.

 

Best regards,

Robin.

To put it another way - show me one incident/accident that occurred because someone failed to enter the winds into the FMS. Good luck.

 

You're not going to...it's a tactical decision aid, not a vital function.  That's like trying to say "find me an accident where the crew used HIGH over AUTO pack flow."

 

...and I was referring to the black and white arguments on the forum lately, not in aviation in general.  Specifically, I was referring to your point that it's a wasted effort.  It's not going to be spot on, but it's not going to be a wasted effort.  There's a reason it's there, and the data the airlines get is digested to include forecasts to points where current reported would be worthless.  Our sim data does not.

 

 

Our sim data does not.

 

Kyle

 

What does this mean?

 

Michael Cubine

 

 

If they were spot on all the time, the weather forecasters would also be spot on their forecasts every time. We all know that's not the truth, so we all have to accept the truth that weather is weather, and it's not always predictable.

 

Guys,

 

Pls keep this thread up as I'm learning a lot by this discussion on weather impact to flight planning.

 

As for the quote above by Kyle, this triggered a memory of a saying I heard once from a  Cruise ship captain...

"It's a forecast, not a contract!!"

 

Regards,

@Kyle: I understand exactly what you're saying about black/white arguments/positions - and I tend to agree.

 

My point was that some people seem to think it is life/death to enter the winds into the FMS, but whilst it may result in more accurate FMS predictions (and this is the reason Michael stated he did it for example), it does not change the parameters used at the flight planning stage.

 

OK - so the FMS figures are more accurate. So what? Actual vs. forecast winds WILL be different. What matters is this: at waypoint ABCDE, does the aircraft actually have the required fuel on board, according to the flight plan, to proceed? The rest is simply monitoring progress (fuel burns/times). If fuel burn is higher than expected, and time between waypoints is higher than expected, then is there a problem? Could simply be due to winds.

 

If the fuel burn is signifiantly higher but time is on schedule, then it is time to start looking at the aircraft, as something is wrong (and this is why these checks are conducted). By significant, I mean if the FP states 1000 lbs, and you burn 1100 lbs - that is a 10% difference in burn.

 

Best regards,

Robin.

 

 

What does this mean?

 

If you look at the data you're getting in most weather programs, the data you're being handed is simply reported winds as they stand now.  Well, if I have a 12 hour flight and I load that current data for the whole 12 hour flight, the farther down the flight plan I enter that data, the more error I'm opening myself up to.  For this reason, it would be better to have current data for the time period until the forecast data picks up.  For NCEP wind forecasts, this is about 7 hours.  So, up to 7 hours into the flight, you'd use the reported/current/now data, and then 7 hours and later, use the forecast data to have better accuracy.  The problem is that the weather programs (to the best of my knowledge) we use in the sim do not do this.  They just pull the reported/current/now data for the entire plan.  So, your the data more than 7 hours into the flight is at a higher risk for error (depending on the stability of the atmosphere).

 

The problem here, though, is that weather has no answer.  Too many people (simmers in particular) look at this like there's some programmatic solution and there really isn't.  As I keep posting in these threads, over and over again: don't get lost in the details, because when you're feeding weather data (particularly anticipated weather data) into the system, you can only put so much weight in it.  It's best not to obsess over it.

 

Weather is weather.  It has the propensity to change.

Notions are good.  Obsessively entering weather into the system in the idea that it's going give you perfect numbers is only setting yourself up for disappointment.

 

Case in point:

Contingency fuel numbers - a recognition by planners and dispatchers that "[stuff] happens," and you just can't predict that.  See: wind.

 

 

@Kyle: I understand exactly what you're saying about black/white arguments/positions - and I tend to agree.
 
My point was that some people seem to think it is life/death to enter the winds into the FMS, but whilst it may result in more accurate FMS predictions (and this is the reason Michael stated he did it for example), it does not change the parameters used at the flight planning stage.

 

Gotcha - we're on the same page.  Good to know.

Flight in MD-11 KOAK-RJBB. ETE  is 11:02 using headwind component of 50 kts at FL360. ETE is 11:26 using entry by waypoint altitude to account for step climbs. Actual time enroute was 11:35. ETA at T/C is 0418Z. ETA at T/D is 0426Z.

 

I have attached a Navigation Log report from ASE which I ran about eight hours after the flight started. I used AS2012 for the flight. The difference is insignificant which can be seen from the headwind component off 48 and 50 knots.  Starting with waypoint ABETS thru GBE the distance travelled is 510 nm of a trip distance of 4853 nm or 11%. In determining  an average wind these six waypoints are will account for 35% of the route. I confirmed with Hi Fi Technologies several years ago that the average component is not weighted for any distance between waypoints. The component is just a simple average. Total the wind for all waypoints and divide by the number of waypoints.This is the fallacy of the component average. The 10 miles after GBE is given the same weight as the 485 mile after 42E60.

 

Great example Michael!

 

Best regards,

Robin.

Robin

 

Thanks for the compliment.

 

The post is not intended to influence how you might enter winds into the MD-11. I hope that I can influence a experienced user or a newcomer to use winds by waypoint if they are wondering how to deal with entering winds into the FMS of the MD-11. Each of us use what method we think works the best while balancing that against the time each method requires.

Even I have used the average component on several flights with a lot of waypoints such as Saigon to Frankfurt which has 91 waypoints. That would simply take too long.

 

Michael Cubine