By: silberstein
- 13th November 2017 at 20:23Permalink- Edited 1st January 1970 at 01:00
The FOI report is probably a terrible source. It's a defense research agency primer on network-centric warfare from 2001 and has very little to do with low-observable aircraft really. The quote about 0.1 sqm RCS is taken from an example on how to handle hostile aircraft incursions from a network perspective, not a detailed case study on stealth. It is stated in the Swedish text that the figures on RCS are "based on experiential evidence from FOI personnel"; given that the example uses 0.1 sqm RCS for a Gripen with a 4 AMRAAM (pre-Meteor)/2 Sidewinder loadout - we would have to assume that these figures are highly speculative if not outright useless. This is, of course, an aside to the case of the missing radar band information :)
By: Vanshilar
- 13th November 2017 at 21:39Permalink- Edited 1st January 1970 at 01:00
Yeah there are plenty of problems with the Saab marketing brochure.
Since when F-35 only carry 2 AAM?
More importantly, who in the world would use that mission profile? It assumes that the plane needs to supercruise to the CAP area, but then it assumes the pilot wants to maximize CAP time. If so, wouldn't it make much more sense to get to the CAP area at cruise speed of around M = 0.8-0.9 so that you're not going full military thrust on the way there and the way back? You're only saving a few minutes anyway by supercruising with this mission profile, but you'd more than make it up with a longer CAP time.
It's stuff like this that makes people not really take the Saab marketing seriously. Sounds good "on paper" to get the results they want, but makes less sense the more and more you think about it.
Compare wing loading and Thrust loading without knowing lift coefficient and equalize combat radius?. No surprised F-15E looks so much better than F-16, F-18
The 2008 RAND report claimed that the scatter plot was based on 50% internal fuel (which disadvantages higher fuel fraction planes like the F-35 and benefits lower fuel fraction planes like the Gripen). But not only that, it arbitrarily added or subtracted weight to different aircraft at whim. For example, it only added about 7400 lb to the empty weight of the F-22 when calculating T:W and wing loading when the F-22 reportedly carries 18,000 lb of internal fuel, plus the weight of weapons. It only added about 8500 lb to the F-15E when it carries over 23,000 lb of internal fuel (including from its CFT's) plus weapons. In other words, not only is "50% internal fuel" a bad assumption for comparing the performance of different planes, the scatter plot itself didn't even adhere to that! If it had, the scatter plot would have shown the F-22 to be "double inferior" (lower thrust to weight, higher wing loading) to the PAK FA, F-15C, and Typhoon, but people would've noticed that and called BS on the plot. So instead the authors arbitrarily changed the loaded weights for each aircraft to get the results they wanted.
My favorite example of this is the MiG-29M. The authors gave it a wing loading of 70 lb/sq ft. Since the MiG-29M has a wing area of 409 sq ft, this means that they assumed its loaded weight would be 70*409 = 28,630 lb. Yet wikipedia (I know, I know...) lists its empty weight as 29,500 lb, so the loaded weight they used for it was even lighter than its empty weight! Now, granted, they might have used the stats for the MiG-29 (rather than the M variant); but the original RAND powerpoint (not the Saab) clearly states it's the MiG-29M, and not only that, the F-35 actually has pretty similar T:W and wing loading as the MiG-29! So any such scatter plot that has the F-35 not very close to the MiG-29 should immediately raise suspicions. But again, they didn't want to admit that, so they just made up numbers until they got the desired results. No wonder why RAND themselves disavowed the report shortly thereafter.
Additionally, at the time, Saab was claiming that the Gripen E would be 15,700 lb empty with 7300 lb internal fuel. As of 2015 they were saying it would be 8000 kg with 3400 kg internal fuel, or 17,600 lb empty with 7500 lb internal fuel, an increase of 12% to its empty weight, with the requisite decrease to its flight performance. Who knows what they're claiming now...
Posts: 1
By: silberstein - 13th November 2017 at 20:23 Permalink - Edited 1st January 1970 at 01:00
The FOI report is probably a terrible source. It's a defense research agency primer on network-centric warfare from 2001 and has very little to do with low-observable aircraft really. The quote about 0.1 sqm RCS is taken from an example on how to handle hostile aircraft incursions from a network perspective, not a detailed case study on stealth. It is stated in the Swedish text that the figures on RCS are "based on experiential evidence from FOI personnel"; given that the example uses 0.1 sqm RCS for a Gripen with a 4 AMRAAM (pre-Meteor)/2 Sidewinder loadout - we would have to assume that these figures are highly speculative if not outright useless. This is, of course, an aside to the case of the missing radar band information :)
Posts: 112
By: Vanshilar - 13th November 2017 at 21:39 Permalink - Edited 1st January 1970 at 01:00
Yeah there are plenty of problems with the Saab marketing brochure.
More importantly, who in the world would use that mission profile? It assumes that the plane needs to supercruise to the CAP area, but then it assumes the pilot wants to maximize CAP time. If so, wouldn't it make much more sense to get to the CAP area at cruise speed of around M = 0.8-0.9 so that you're not going full military thrust on the way there and the way back? You're only saving a few minutes anyway by supercruising with this mission profile, but you'd more than make it up with a longer CAP time.
It's stuff like this that makes people not really take the Saab marketing seriously. Sounds good "on paper" to get the results they want, but makes less sense the more and more you think about it.
The 2008 RAND report claimed that the scatter plot was based on 50% internal fuel (which disadvantages higher fuel fraction planes like the F-35 and benefits lower fuel fraction planes like the Gripen). But not only that, it arbitrarily added or subtracted weight to different aircraft at whim. For example, it only added about 7400 lb to the empty weight of the F-22 when calculating T:W and wing loading when the F-22 reportedly carries 18,000 lb of internal fuel, plus the weight of weapons. It only added about 8500 lb to the F-15E when it carries over 23,000 lb of internal fuel (including from its CFT's) plus weapons. In other words, not only is "50% internal fuel" a bad assumption for comparing the performance of different planes, the scatter plot itself didn't even adhere to that! If it had, the scatter plot would have shown the F-22 to be "double inferior" (lower thrust to weight, higher wing loading) to the PAK FA, F-15C, and Typhoon, but people would've noticed that and called BS on the plot. So instead the authors arbitrarily changed the loaded weights for each aircraft to get the results they wanted.
My favorite example of this is the MiG-29M. The authors gave it a wing loading of 70 lb/sq ft. Since the MiG-29M has a wing area of 409 sq ft, this means that they assumed its loaded weight would be 70*409 = 28,630 lb. Yet wikipedia (I know, I know...) lists its empty weight as 29,500 lb, so the loaded weight they used for it was even lighter than its empty weight! Now, granted, they might have used the stats for the MiG-29 (rather than the M variant); but the original RAND powerpoint (not the Saab) clearly states it's the MiG-29M, and not only that, the F-35 actually has pretty similar T:W and wing loading as the MiG-29! So any such scatter plot that has the F-35 not very close to the MiG-29 should immediately raise suspicions. But again, they didn't want to admit that, so they just made up numbers until they got the desired results. No wonder why RAND themselves disavowed the report shortly thereafter.
Additionally, at the time, Saab was claiming that the Gripen E would be 15,700 lb empty with 7300 lb internal fuel. As of 2015 they were saying it would be 8000 kg with 3400 kg internal fuel, or 17,600 lb empty with 7500 lb internal fuel, an increase of 12% to its empty weight, with the requisite decrease to its flight performance. Who knows what they're claiming now...