Teach me why I listen to Turboprop drivers always discussing airspeed.

[Hugh Johnson]

I think it is because they have been flying Navajo's, Seneca's and Barons, and this is their first Turbo Prop.

 

[can99]

OK tell me the aerodynamics and formulas to come up with NIL wind figures gives you a lower GS for a known TAS:

IE you say TAS 415 = GS 385 !

My understanding of ground speed is thats its the speed of an aircraft relative to the ground. It is the sum of the aircraft's true airspeed and the current wind... teaching and writing texts books for the last 20 years on this crap may have fried my brain but a 400kt TAS with no wind is a 400kt GS?


Unless I am wrong and missed something here.

 

[400A]

I think it is because they have been flying Navajo's, Seneca's and Barons, and this is their first Turbo Prop.

Very true. We should not be so quick to forget the excitement of a new milestone.

 

[hmmm]

Not exactly true. The higher you go in a jet the slower your groundspeed will be once you past the point of max rated power.

EX.. assuming winds are calm.

31,000 ft. TAS 425, GS 400, Fuel Flow 2,000 PPH
38,000 ft. TAS 450, GS 425, Fuel Flow 1,500 PPH
43,000 ft. TAS 415, GS 385, Fuel Flow 1,000 PPH

I feel the same way you do. I hear pilots all the time talking about TAS, etc. I could care less. I only look at GS also. But, as stated above, for performance mods etc, it is the only way to compare, and you really cant control GS.

Yes I look at it the same way.... We are looking for the best distance gone over the ground compared to least amount of fuel flow.....................could be higher or lower depending on the situation, variables, time of day traffic, possible holds, whether ATC's hair looked nice in the mirror today, and how much viagra the captain used the other day even if we are the captain...........................of course beyond all the theoretical bull we learn about in training throughout the years........ it all depends on -everything- temps, ice protection bled off the engines, how fast we want to get there and do we want the engines to quit once we touch down from fuel exhaustion, owner and passenger likes or comfort, turbulence and penetration speed etc etc etc. No need for book worms to jump up and down on their soap box.... this is about real life and monitoring the plane a nd tweaking your performance as a human not a computer.

 

[can99]

No need for book worms to jump up and down on their soap box.... this is about real life and monitoring the plane a nd tweaking your performance as a human not a computer.

Ummmm in real life if you cant understand the relationship between something as simple as tas and gs you really should rethink all that theoretical bull you learnt again...it might come in handy one day!

 

[siouxicide]

Recommended reading for all that don't understand TAS:
True airspeed defined Check out the second sentence.

 

[cvsfly]

Hey...

Someone please teach me why I listen to Turboprop drivers always discussing airspeed.

.....

GS matters to me when I'm flight planning before a flight and during the flight. TAS matters to me if I was discussing performance of a flight after the fact. Talking about what GS you made with someone after the fact - other than bragging rights for a tailwind or aggravation of the fuel bill for a headwind - means very little beyond that. It tells me nothing about the aircraft performance unless I know the exact winds aloft you had. You could of had the power pulled back truing at 200 kts with a 50kt tailwind or you could be at normal cruise truing at 270 kts with a 20kt headwind. Very relative number is GS. TAS with no wind = GS.

 

[kingairyahoo]

bah humbug...its all relative

how heavy are ya? how far are you going? whats ATC gonna do to ya? is it an owner flight or a charter leg? what are the temps? what are the winds doing at the anticipated flight levels? are you taking AK47 rounds from the top of hills while trying to gain altitude leaving FOB Ripley, forcing you to fly down the valley in an underpowered B100 with 10 dam warrant officers onboard who have nothing better to do than overload your airplane...thread creep

back on topic...www.fltplan.com, for the win :beer:

 

[hmmm]

Ummmm in real life if you cant understand the relationship between something as simple as tas and gs you really should rethink all that theoretical bull you learnt again...it might come in handy one day!

Don't need to say much to that.

Lets see so far had 6 engine failures, a cockpit fire, loss of 3 gens 4 nose gear malfunctions, loss of two hydraulics sysytems and

oh never mind I must not be as experienced.

Oh by the way... Why are we talking about TAS I never asked about that.

Indicated, True what ever. The only thing that matters is the one on the dial or tape and how fast your moving toward destination compared to fuel burn.

Oh my gosh without TAS the airplanes going to fall out of the sky.

Yeah Ok We are sure you know all about it and without it nobody can handle their job.

Therefore I guess without you the world would stop spinning.

Oh and isn't fltplan.com wonderful!!!

 

[guido411]

I think I'm going to have to take issue with that. I don't have much time in King Airs, but the Metros and Jet Streams that I flew had tons to gain by climbing.

First, I can rarely reach 100% torque on any given day. So, flying at 100% power just isn't an option.

I have the opposite of your experience and have only flown turboprops with PT-6s. Every single one of them are able to make 100% Tq at SL because they are "flat- rated". They may be capable of producing twice as much HP as they are rated for (thermodynamic power) but are limited to a lesser amount.

If the engine was not flat-rated it would only make 100% rated power at SL. The Pratt TP airplanes I have flown have all maintained 100% Tq up to a certain altidue where either the power levers had no travel left or temperature (ITT) was at it's max allowable for climb/cruise. THAT is the optimum altitude for that particular airplane when referencing TAS (fuel flow is another consideration that only the pilot [or owner] can weigh the imprtance of).

So I say again slightly re-stated, the best altitude (if you want to brag about how fast your PT6 soot-streaker goes) is the highest altitude attainable where your engine is still producing 100% of it's rated power.

 

[siouxicide]

Since you started thumping your chest, I just had to:

Now I have been around all sorts of airplanes forever. Worked on just about everything including being a jet and turboprop engine overhaul guy and inspector

Lets see so far had 6 engine failures, a cockpit fire, loss of 3 gens 4 nose gear malfunctions, loss of two hydraulics sytems

Coincidence?

As a pilot I care about is my speed across the ground depending on the altitude in still air....

That's the definition of True Airspeed, more or less. Because you spelled it out the hard way, it tells me you didn't know that.

The only thing that matters is the one on the dial or tape....

And that would be Indicated Airspeed. Why the contradiction?

 

[hmmm]

oh boy

 

[Morettis]

I'm going to second that the best altitude isn't always the highest you can get to.

The Metro I fly gets the best TAS at FL190 and FL200. I also get a huge fuel drop from 17,000 to FL190 but virtually no drop above FL200. I can go to FL300 (if I had RVSM) but I lose about 30 kTAS.

So, when you hear KA pilots talking airspeed (guessing its TAS) at certain altitudes, they are just comparing their best performance.

Last I checked, the book says the best TAS for a metro is in the 10-15k range depending on temperature and weight. Best TAS comes at the highest altitude that you can hold the barber pole.

 

[ksu_aviator]

Last I checked, the book says the best TAS for a metro is in the 10-15k range depending on temperature and weight. Best TAS comes at the highest altitude that you can hold the barber pole.

If all you are worried about is TAS, than you are probably right. But I'm using numbers for best fuel burn to TAS ratio.

 

[woog315]

With winds calm, I get about 260K TAS from 12k - ~22k at 100%rpm and max torque, obviously i head up to 220 for the increased fuel savings. Also, I don't agree with the guy who said he sees little fuel savings above 190, I drop an extra 75-125lbs/hr going from 190 to around 230 with no ground speed reduction

edit: it probably depends on how long your legs are if climbing above 190 is worth it as the metro tends to bog down around there. I'm frequently on 4-5hr legs so it's worth it for me.