SAAB Gripen and Gripen NG thread #4

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@hopsalot ".. and what is the Gripen NG's supersonic range?"

http://techworld.idg.se/2.2524/1.174315/reaktionsmotor-12---bade-vacker-och-stark

According to this article Gripen c dry thrust is 1.2kg/s and afterburner is 4kg/s. Ill give you the engine burn times dry and wet Measured on rm12 but with the gripen E's fuel(internal).
This is only theoretical max burns. And with not exactly (but very close to, engine).
Full dry thrust maximum burntime = 1.2kg/s*60=72kg/min. Internal tank on E version is 3400kg/72kg=47,2 minutes
Full wet thrust maximum burntime= 4kg/s*60=240kg/min. 3400kg/240=14,16 minutes

Ill give you an example......
Now if you max dry thrust a gripen e , it will fly somewhere between mach 1.1 mach 1.25 depending on load of stuff BUT having started with say two droptanks (subsonic), which where dropped before engagement and returning back with pretty much full tank.
It is very likely that Supercruising back for say 47,2 minus 12 minutes for safety ...35minutes would be quite possible. With the result in a quick and IR-low return and rearm. The range with mach 1.2 (having left the battle and all) is converted to 1468kph.
So 35 minutes would be 856,3km flown. Super cruise on internal one direction.


That calculation is wrong, Thrust specific fuel consumption varied significantly with altitude and speed
http://www.f-16.net/forum/download/file.php?id=21187&t=1
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That calculation is wrong, Thrust specific fuel consumption varied significantly with altitude and speed

If it's wrong, then make corrections.. Nobody has time to study the myriad of graphs you tend to post.

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If it's wrong, then make corrections.. Nobody has time to study the myriad of graphs you tend to post.

If you read the post carefully, you will realize that i already made correction (point out where he is wrong) , and the graph is rather simple for most people to understand what it say

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Pointing out where someone is wrong does not suffice. Either you got a better calculation that he has or you got nothing..

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Pointing out where someone is wrong does not suffice. Either you got a better calculation that he has or you got nothing..

Very funny that you change your stand now, given the fact that you often have the habit of never backup what you said with calculations
Just because i didnt give a number of my own doesn't mean what i say was wrong, his calculation is ridiculous regardless, i didn't give any number due to the fact that none of us know the dynamic thrust of Gripen NG at altitude and mach 1.2 so any so called " calculation" are 85% BS or bias

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Let say TSFC of F414G at mach 1.2 is 2 lb/(h. · lbf)
Gripen NG internal fuel load is 7300 lbs
dry thrust is 12000 lbs
[7300/ (12000*2)] * 60 = 18 minutes
however you need fuel to take off, landing, climb, accelerate, ( and may be even dogfight)
so IMHO, Gripen NG realistically only has enough fuel to supercruise for around 10 minutes (will be less when including subsonic cruise)

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@mig-31bm
So because you add other factors in, the calculations are wrong ? Allow me to smile. I also pointed out theoretical part of it.

You are right that the consumption increases, but it is an lesser problem for an aircraft with and smaller engine that has less consumption. Because they in general draw much less fuel.
Its also a lesser problem for aircraft made to super cruise and supersonic flight from the beginning.

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Let say TSFC of F414G at mach 1.2 is 2 lb/(h. · lbf)
Gripen NG internal fuel load is 7300 lbs
dry thrust is 12000 lbs
[7300/ (12000*2)] * 60 = 18 minutes
however you need fuel to take off, landing, climb, accelerate, ( and may be even dogfight)
so IMHO, Gripen NG realistically only has enough fuel to supercruise for around 10 minutes (will be less when including subsonic cruise)

Wrong ! Internal tank on E version is 3400kg/72kg=47,2 minutes split in two that would be 23,6 minutes. And remember we are talking maximum dry thrust here. what sfc (grams) are you using ? Link?

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using static fuel consumption under afterburner to calculate consumption
under military power at height where consumption goes down wtf ??!

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That calculation is wrong, Thrust specific fuel consumption varied significantly with altitude and speed
http://www.f-16.net/forum/download/file.php?id=21187&t=1

If that is specific fuel consumption then it is wrong.
SFC= lb fuel/lb thrust/ hr
Most gas turbines run at around 0.6-0.7 until reheat is engaged. That increases total thrust but also has a poor thermal efficiency, ergo, the SFC is worse.
TOTAL fuel consumption is dependent on engine rpm (pressure ratio), altitude (amplification ratio) and velocity (drag rule/ram effect).
That graph looks at best suspect, probably something cooked up by someone who has heard a bit and thinks he knows....
Data is normally gathered by tests carried out on altitude test-beds or by flight tests. Nowadays, after so much research they do not have to test as rigorously as they did decades ago, merely confirm knowledge previously and expensively garnered. These figures are empirical and in general unpublished to the public....
Your graphs and figures are therefore by virtue, without value. who actually plots these graphs, someone who works in the business or someone who would like to?

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SFC= lb fuel/lb thrust/ hr
Most gas turbines run at around 0.6-0.7 until reheat is engaged.

So ball park fuel burn figure for 12,000 lb thrust is 7,200lb-8,400lb per hour? Gripen can maintain supersonic speed on 12,000lb thrust with a minimal drag load (eg 2 x A2A missiles). What supersonic speed does the aircraft need to reach before transonic drag starts to reduce?

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how long a fighter will remain in transonic is very different from fighter to fighter,
depending on wing sweep, area distribution, wing thickness, etc,
deltas are as built for transonic, out of current fighters, gripen is hard to beat, only competition being possibly EF,
F-16 exit around M1.15, gripen & EF around M1.05, F-35 somewhere after M1.2
http://history.nasa.gov/SP-367/f91.htm
http://history.nasa.gov/SP-367/chapt5.htm

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how long a fighter will remain in transonic is very different from fighter to fighter,
depending on wing sweep, area distribution, wing thickness, etc,
deltas are as built for transonic, out of current fighters, gripen is hard to beat, only competition being possibly EF,
F-16 exit around M1.15, gripen & EF around M1.05, F-35 somewhere after M1.2
http://history.nasa.gov/SP-367/f91.htm
http://history.nasa.gov/SP-367/chapt5.htm

Sigh, your "analysis" would have been better served to just simply point out aspects of the Gripen design favorable to transonic drag reduction. When you started putting numbers on various aircraft, it becaume a fail.

As you pointed out, there are several factors to consider when assessing wave drag. Low aspect ratio and the use of supercritical wings make guessing wave drag based on sweep angle a fools game.

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Sigh, your "analysis" would have been better served to just simply point out aspects of the Gripen design favorable to transonic drag reduction. When you started putting numbers on various aircraft, it becaume a fail.

obligatory answered my question well enough. Just wanted some guidance. That is what I got. The deltas - Gripen, Typhoon (and presumably Rafale) - appear more favourably shaped for lower supersonic speed transonic drag reduction. I wonder if they win on subsonic transonic drag, too.

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obligatory answered my question well enough. Just wanted some guidance. That is what I got. The deltas - Gripen, Typhoon (and presumably Rafale) - appear more favourably shaped for lower supersonic speed transonic drag reduction. I wonder if they win on subsonic transonic drag, too.

Delta wings have higher drag overall, they are less efficient at subsonic speeds, but have the benefit of higher critical mach. If Obligatory's answer suits you, fine. But it is deficient in the assumption that having a delta wing is the primary factor in reducing transonic drag. (Think YF-102)

The numbers.... like mach 1.05? contrived out of thin air.

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@mig-31bm
So because you add other factors in, the calculations are wrong ? Allow me to smile. I also pointed out theoretical part of it.

The things is , the factor i added in will change the result significantly not just a little bit
You are right that the consumption increases, but it is an lesser problem for an aircraft with and smaller engine that has less consumption. Because they in general draw much less fuel.

They also carry much less fuel in the first place

Its also a lesser problem for aircraft made to super cruise and supersonic flight from the beginning.

Not really , if all operate in dry thrust ,then engine of supercruise aircraft will often be more thirsty ( low bypass ratio , run mostly with the core )

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Wrong ! Internal tank on E version is 3400kg/72kg=47,2 minutes split in two that would be 23,6 minutes.

according to this imagine from SAAB internal fuel load of Gripen E is 7300 pounds
https://thaimilitaryandasianregion.files.wordpress.com/2015/10/gripenng_holanda_specs_2009.jpg
And remember we are talking maximum dry thrust here. what sfc (grams) are you using ? Link?

I think he just scale it up from the graph
using static fuel consumption under afterburner to calculate consumption
under military power at height where consumption goes down wtf ??!

at the same speed , then consumption will go down as you go higher , but if you increase your speed then fuel consumption will increase

SFC= lb fuel/lb thrust/ hr
Most gas turbines run at around 0.6-0.7 until reheat is engaged.

not at all speed and altitude though

Your graphs and figures are therefore by virtue, without value. who actually plots these graphs, someone who works in the business or someone who would like to?


these people
http://www.f-16.net/forum/download/file.php?id=21188&t=1&sid=da30ff65c7c5c5aa796849bb81cd25b6
http://www.f-16.net/forum/download/file.php?id=21189&t=1&sid=da30ff65c7c5c5aa796849bb81cd25b6

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according to this imagine from SAAB internal fuel load of Gripen E is 7300 pounds


According to this link from Saab internal fuel of Gripen NG is 3400 kg:

http://saab.com/globalassets/commercial/air/gripen-fighter-system/gripen-for-brazil/pdf-gripen-ng/gripen-ng-brochure.pdf

Not that the difference between 7300 lbs and 3400 kg is huge... (195 lbs or 88 kg, or 2.5%)

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So ball park fuel burn figure for 12,000 lb thrust is 7,200lb-8,400lb per hour? Gripen can maintain supersonic speed on 12,000lb thrust with a minimal drag load (eg 2 x A2A missiles). What supersonic speed does the aircraft need to reach before transonic drag starts to reduce?

Good questions, the first sounds about right. The second, dependent on the design. They understand the research carried out by Whitcomb and kuchemann and make use of their discovery.
Do remember though that supercruise doe allow them to run longer. due to not using the reheat. An old example of the difference. A Lightning F3 would have about 45 minutes of flight not using the reheat much (take off). Full reheat, about 7 minutes..... We once tested an F6 (Bigger tank) at full reheat for 5 minutes on the ground. It went from full to almost empty.
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obligatory answered my question well enough. Just wanted some guidance. That is what I got. The deltas - Gripen, Typhoon (and presumably Rafale) - appear more favourably shaped for lower supersonic speed transonic drag reduction. I wonder if they win on subsonic transonic drag, too.

yes, it both delay transonic region and end it earlier,
an F-35 would be stuck in transonic from ~M0.8 -M1.2+
while gripen encounter a small jump from M0.95-M1.05,
or thereabout.

the chief designer of gripen suggest a tail configuration improve range at cruise speed,
at least with the info & tech that was available when gripen was designed.

Gripen analyzed

The choice of configuration, canard or tail, was far from obvious, initially.
A substantial body of knowledge existed on the delta canard layout,
gained from Viggen experience of course, but that was not entirely favourable for such a solution.

The drawbacks as well as the good features were evident.
A sometimes heated debate on this topic had been going on inside the Swedish aeronautical community for years.
Wind tunnel testing and project work on alternative aft tailed configurations had pointed out many advantages for that particular layout,
where perhaps range and sustained turn rate were the most noticeable, granted the technological level of that time.


http://www.mach-flyg.com/utg80/80jas_uc.html