Airspeed column on Aircraft Tracking


#1

It would be pretty cool for me if there was an airspeed column on the aircraft tracking page. I know it would not be a true representation of an average speed because some planes are climbing and some descending, but you could take all the airplanes of one type and get pretty close to an average speed for that type. For instance, today looking at the Citation X there was a plane doing 508kts and another doing 531kts within 1000’ of each others altitude. I thought it would be fun to see all airborne C750’s speeds. Anyways, just a thought and extra column on the aircraft type tracking page. Of course, with speed many want altitude too. Is it Pandora’s Box?? hehe. See you guys.


#2

As a representation of a certain type’s average speed, it wouldn’t work. Because of tail and headwinds, the ground speed can differ by hundreds of knots.


#3

I still would like the ability. For instance, my airplane flies somewhere between 170kts and 200kts on average. Really if I took the last 10 flights and ‘averaged’ them, I could reasonably come up with the ‘average’ speed that my plane flies. Let’s simplify to three flights 1st flight [178kts], 2nd flight [170kts] and the 3rd at [198kts]. Let’s also pretend that they were all flown at 6000 - 7000 feet in differing weather conditions. That means we could add them together [178+170+198] to come up with [546kts] total ground speed. We could divide them by [3] the number of flights we took and come up with [182kts].

Ok, so you didn’t need an explanation on how ‘averages’ work. But back to the point. If I did that for the last, say, 30 flights, I could reasonably, probably statisically, come up with the most probable speed that my plane would fly. Wether or not I would be on the money every time that I flew with the airspeed that I averaged is not important. What is interesting to me is that I would be, if the sample was large enough, able to predict with a high confidence what the groundspeed of my airplane would be on any given trip. I could then say, again with a high confidence, that a given trip would take me a specific amount of time to fly.

It may be helpful in planning 135 operations in a given plane at any point regardless of head/tailwinds because of the probability of an established groundspeed that you could calculate by averaging the plane(s) over the course of the day/flights. Also and more importantly, it would give me some enjoyment to be able to look at a make/model of an aircraft and say that the average speed of that make/model is going to be pretty close to what I would calculate from the help of flightaware.com and it’s flight tracking ability.

If you would like to continue to share with me your thoughts on head/tailwinds and the inaccuracies of the calculations, I will be glad to share with you my thoughts on the statisical accuracy in which you could calculate an proposed speed at which you could expect to travel in a specific make/model of an aircraft.

Thanks for your response. It helped me feel better about my assumption of ‘average’ airspeed.


#4

Why don’t you just use the published cruising speed of your aircraft? :confused:

And thanks for the little math lesson, took my mind off triple integrals and paraboloids for the time being. :wink:


#5

hahaha. glad I could help. triple integrals and paraboloids are pretty distacting!! :laughing:


#6

You seem to be confusing airspeed and groundspeed. They are not interchangeable. A couple of points:

There is no way for FA or ATC to determine airspeed of any airplane it is tracking. Since radar is watching from a fixed ground location, it can only determine speed relative to the ground.

Every individual airplane will fly at the same airspeed every time under the same same conditions. Tables of the conditions are listed in the POH. At a certain air temp and pressure (Density Altitude) an airplane of a certain weight and center of gravity (CG) will fly at the same airspeed every time if the same power is used.

Differences between POH airspeed values and actual values are influenced by airframe modifications and condition and are constant under the same conditions (mostly DAlt) until there is a change in them.

Given the fairly large range of speeds you mentioned there must be differences in one or more of the following: DAlt, weight, CG or power. Averaging your speeds would be grossly inaccurate since you aren’t taking into consideration those factors above. Airspeed planning is a factor of preflight planning using the POH tables and applying a correction factor for airframe condition. You should theoretically do this planning before every flight.

It will not help any confidence in the least bit! Groundspeed is a factor of winds aloft and there is no way to average that from a historical point of view. They change in intensity and direction at every altitude by the minute.

Once you determine the planned airspeed mentioned above, you must apply the forecast winds aloft at your cruising altitude. Your airspeed will be dead accurate if you planned properly, but your groundspeed will be only as good as the wind forecast. That’s usually pretty close, but never exact, and can sometimes be far different than planned!

For ballpark planning before you know all of the factors for actual flight planning, most pilots just use the airspeed for a typical altitude on a standard day with no wind. On most trips that will be fairly close for a round trip on any day because the headwind one way becomes a tailwind the other (ignoring quartering wind factors). So the leg in one direction will be longer or shorter than the other, but the total round-trip flight time will be fairly close.

If you want to be conservative (which is safer) subtract 15-30 knots from the typical airspeed to allow for average winds. But this is only a fudge-factor. You will have to do real-time, detailed flight planning when you get your commercial license and fly 135. You should do it anyway for part 91 flying.

Certainly don’t use FA for that purpose! You cannot know from FA what factors are affecting an airplane during any given flight. As mentioned, FA cannot give you the current airspeed of a flight, only groundspeed. You have no way of knowing if the pilot is chosing to fly at an atypical airspeed. It’s the same argument on why FA does not publish estimated arrival times, they publish the planned arrival time based on the actual departure time plus the pre-planned flight time.

You can only know typical airspeeds by research and experience with different models. You can find performance information in a number of places. This table give ATC planning figures for climb, decent, and hold short.. I’ll let you do your own research to find typical airspeeds for different models. Trust me, they are out there! Have fun!


#7

Forget all the hullabaloo. :unamused: I am wrong and I don’t mind being wrong. I will check the link in the last post for the speeds published by the FAA. I still would like the column for the real reason — seeing what the real groundspeeds of planes like C750 and H25B are. Forget the fact that I care about what my Cirrus goes and how accurate I can ‘average’ speeds. I just want to have some fun looking at the fastest business jet on the planet and say ‘hell yeah, that’s fast’. Then look at all of them airborne and say ‘there’s the fastest one in the nation right now’. It may seem, even to me now, that I have some other motive - flight planning, 135 averages, statistical/imperial data - nope. Just want to see how fast they are going when I look at them. Anyone else onboard for that?


#8

You know, you could have saved me a lot of time if you had said that in the beginning. I spent over an hour writing that response because I was trying to help, missing plans to go flying myself in the process. You either don’t know the difference between airspeed and groundspeed or don’t care to use the correct term when you type.

That link doesn’t have speeds, I did that on purpose. But there are some out there if you look.

You can’t get airspeeds from radar. The “real groundspeed” is right there in front of you. I’m sorry I wasted my time.


#9

:frowning:

didn’t start out by devising a plan to waste your time. i appreciate your earnest attempt to explain my request. I truly am sorry. :blush:

do you think that showing the speeds right there on the page with aircraft tracking would be cool or whatever it would be considered? It is difficult to click every page of a plane in the air to get their speed. Perhaps a more comprehensive page could be created and a link be put on at the bottom of the page for tracking. or maybe even an excel data file.

i do appreciate your interest.


#10

Dang, Mr. Taylor. If it ruined your day to write a knowledgeable post, now I hate that I wasted my time enjoying it. Please don’t waste our time telling us how much you hated writing things.


#11

:laughing: I do feel like Mr. Taylor could get me my private, instrument, commercial, ATP online now though. I’m ready for a G550 full of people after his post. Happy Flying. --(+)-(’ ')-(+)–


#12

Well, I guess I’ll have to retract my comment. I must have been feeling sorry for myself yesterday (it wasn’t a good one).

I’m glad you may have gained something from my post. I don’t know nearly as much as some people, but I do enjoy sharing what I can.

I’ll quit wallowing my self-pity and get on with it. :slight_smile:


#13

If the purpose in knowing average ground speed is to improve an estimate of planned time of arrival, even that is filled with ‘loopholes’. First, of course, is wind speed/direction variability at each altitude. Second is routing variability. One is not flying ‘great circle’ paths between A and B. Alternative routes might add as much as 20% to flight distance and hence flight time. Finally we get to the pair of dice in the sky – weather system diversions and traffic holding patterns. I’m looking forward to Texas tornado season to see what happens to flight paths. Furthermore, because of this, you can’t simply divide distance between airports by flight duration to get an average ground speed. For flights with wide routing swings and lots of holding loops before clearance to land, the average ground speed might even be lower that the engine stall speed. You’d have to know the actual mileage flown – a value not available here at this time.

Btw, thanks to BTaylor for his erudite essay on air speed. I read it and didn’t for a second think I was wasting my time.