J-20 versus F-35

gta4 · by **gta4** » 16 Jun 2018, 13:28

First, we should define what "operational empty weight" (OEW) includes. Does it inclue pilot? gun-ammo? launchers? pylons? missiles? CFTs?

Secondly, we should not apply different standard when comparing aircraft performances. From Sukhoi website a single seater flanker takes-off at 23430 kg with 5270 kg fuel, 2 R73s and 2 R27s, which gives it an OEM of nearly 17500 kg. However, the single seater flanker is always reported to have an empty weight of 16400 kg on some forums or websites. That is not fair. That is not OEM, but "recovery weight" by US standard.

A single seater super hornet has a recovery weight of 30564 lbs and an OEM of 31500 lbs. A way to verify this: from Super hornet block II flight manual, the total fliying weight of a super hornet with 5 AIM-120s and 2 AIM-9s and a FLIR pod and 60% internal fual is 43768 lbs (5 AIM-120s + 1 pod means 2 tripple launchers are used). A double seater super hornet has an OEM of 32000 lbs, which is always confused by some amateurs as the empty weight of single seater.

basher54321 · by **basher54321** » 16 Jun 2018, 13:30

Standard Aircraft Characteristics - the original document is dated Feb 1992

There is another one from the same year with CFTs with empty weight as 30,963 lbs but not seen anything later on that front.

fbw · by **fbw** » 16 Jun 2018, 14:02

gta4 wrote:First, we should define what "operational empty weight" (OEW) includes. Does it inclue pilot? gun-ammo? launchers? pylons? missiles? CFTs?

Secondly, we should not apply different standard when comparing aircraft performances. From Sukhoi website a single seater flanker takes-off at 23430 kg with 5270 kg fuel, 2 R73s and 2 R27s, which gives it an OEM of nearly 17500 kg. However, the single seater flanker is always reported to have an empty weight of 16400 kg on some forums or websites. That is not fair. That is not OEM, but "recovery weight" by US standard.

A single seater super hornet has a recovery weight of 30564 lbs and an OEM of 31500 lbs. A way to verify this: from Super hornet block II flight manual, the total fliying weight of a super hornet with 5 AIM-120s and 2 AIM-9s and a FLIR pod and 60% internal fual is 43768 lbs (5 AIM-120s + 1 pod means 2 tripple launchers are used). A double seater super hornet has an OEM of 32000 lbs, which is always confused by some amateurs as the empty weight of single seater.

Operating empty weight includes unrecoverable fuel, lubricant, aircrew, sometimes countermeasures. It does not include weapons, pods or any of those things above.

I don’t know when your F-15C manual is dated from, the 1985 flight manual states 29,000 OEW. That was pre-MSIP II. Aircraft gain weight over time. Boeing and the USAF had F-15 OEW as 31,700 and the F-15E with CFT as 37,500, which is interesting because the “C” is now near the original empty weight of the F-15E. The AESA adds weight as well. One indication of how much weight the f-15 has gained is that Boeing considered removing the the ballast in the nose as aircrafts C.G. had shifted over the years (actually this was flight tested many years ago, Pre-Boeing). Addition- post Boeing, and it was simulated, a war college paper (1991) weight ~29,000 lbs. author does not list MSIP II upgrades in avionics weight changes though.
http://www.dtic.mil/dtic/tr/fulltext/u2/a244044.pdf

Edit- interestingly AvWeek too lists the F-15C’s empty weight as 31,700 and the “E” without CFT as 33,070. In short, I don’t think we’re going to get a completely accurate updated weight, but it certainly does not weight the same as it did 27 odd years ago. Those numbers above look reasonably accurate, as i went back and referenced the 1993 F-15E flight manual and it listed OEW without CFT as 33,500 and with at 37,500.

gta4 · by **gta4** » 16 Jun 2018, 16:59

When computing air combat performance, CFT should not be included, and you are using f15c's weight with CFT to compare against a 15e without CFT.

fbw · by **fbw** » 16 Jun 2018, 17:05

gta4 wrote:When computing air combat performance, CFT should not be included, and you are using f15c's weight with CFT to compare against a 15e without CFT.

Where are you getting that idea from? The F-15C weights I listed don’t include CFT, why would they? The F-15C’s empty weight (without CFT) was roughly 29,000lbs pre MSIP II and APG-63(v)3. That was 27 years ago. The USAF lists OEW as 31,700. That should give you a good idea how much weight the F-15C has gained over the years.

elvis1 · by **elvis1** » 16 Jun 2018, 17:47

I too have gained a bit of weight since 1992 :oops:

. It is nice to know it also happens to jets!

spazsinbad · by **spazsinbad** » 16 Jun 2018, 20:29

elvis1 wrote:I too have gained a bit of weight since 1992 . It is nice to know it also happens to jets!

Thanks for that. :mrgreen:

Elvis HAS NOT LEFT THE BUILDING! :roll:

gta4 · by **gta4** » 16 Jun 2018, 23:06

Just paste a reliable source of 31700 lbs.

I have only seen 30700 lbs, not 31700 lbs.

Fred Clifton (f15 16 fulcrum pilot ) lists F15C to have only gained 1500 lbs compared to F15A in a recent interview.

fbw · by **fbw** » 17 Jun 2018, 00:24

gta4 wrote:Just paste a reliable source of 31700 lbs.

I have only seen 30700 lbs, not 31700 lbs.

Fred Clifton (f15 16 fulcrum pilot ) lists F15C to have only gained 1500 lbs compared to F15A in a recent interview.

Official enough for you? ( if that’s not good enough I have two more) That’s OEW which is generally 600-800+lbs over empty weight (probably on the high side for a twin engine aircraft)
http://www.af.mil/About-Us/Fact-Sheets/ ... -15-eagle/

Exactly, the latest F-15C have added at least 1500lbs of structural weight and equipment. You were stating 28,400lb empty weight. What I was showing you all along was that the OEW showed an “empty” weight over 30,000lbs.

That took four posts, when only one was needed. Obviously an aircraft that weighed 28,400 in 1992 and then added OBOGS, GPS, JTIDS, an AESA array and associated equipment isn’t going to weigh the same it did then.

And for reference, manufacturer’s empty weight is pretty irrelevant after the aircraft has been in service for years. The average weight growth is 5% and up, and there is considerable variation within a fleet.

gta4 · by **gta4** » 17 Jun 2018, 00:52

Without knowing what is included in the 31700 lbs, it makes no difference with 30700 lbs.

I have plenty of official data showing a post msip F15C at 30700 lbs includes everything except usable fuel and missiles.

fbw · by **fbw** » 17 Jun 2018, 00:55

gta4 wrote:Without knowing what is included in the 31700 lbs, it makes no difference with 30700 lbs.

I have plenty of official data showing a post msip F15C at 30700 lbs includes everything except usable fuel and missiles.

Great, what did my OP say? “It’s been a long time since the F-15C weighed under 30,000lbs” . Then I gave you the definition for OEW (unusable fuel, engine lubricant, crew, (sometimes) chaff/flares, 20mm shells, etc). Does not include pylons, weapons, etc.

Get it?

gta4 · by **gta4** » 17 Jun 2018, 00:59

Calculating aircraft performance is very sensitive to weight changes. You need to be cautious.

We know what a 30700 lbs F15C includes, but we don't know what a 31700 lbs F15C includes. What if it already includes launchers and missiles and gun ammo and pilot (like the F16Block52+ manual), and you count it twice in T/W ratio calculation? That is unfair.

fbw · by **fbw** » 17 Jun 2018, 01:03

gta4 wrote:Calculating aircraft performance is very sensitive to weight changes. You need to be cautious.

We know what a 30700 lbs F15C includes, but we don't know what a 31700 lbs F15C includes. What if it already includes launchers and missiles and gun ammo and pilot (like the F16Block52+ manual), and you count it twice in T/W ratio calculation? That is unfair.

It doesn’t. One, I have seen zero information post 1992 for an empty weight of 30,700 (or any empty weight other than OEW since then and won’t unless an updated flight manual becomes available). What you are listing probably refers to basic aircraft weight. You need a pilot yes? Countermeasures are always carried, as is 20mm (though not a full load). And if you think about it, the numbers add up 300lbs of 200mm, 180lb pilot, few hundred pounds of countermeasures, etc.

The number on the fact sheet is accurate, if you doubt it look up the fact sheet for the F-15E and compare it to the flight manual (pretty much spot on).

gta4 · by **gta4** » 17 Jun 2018, 01:06

Sorry man, there is no strict OEW deffination. It may vary with different aircrafts.

I have plenty of F16 flight manual showing OEM with missiles and launchers.

fbw · by **fbw** » 17 Jun 2018, 01:09

gta4 wrote:Sorry man, there is no strict OEW deffination. It may vary with different aircrafts.

I have plenty of F16 flight manual showing OEM with missiles and launchers.

Ok, refer to your first post. Do you still think the F-15C weighs under 30,000lbs empty/dry? If so, I can’t help you.

P.s. adding the wing pylons and C/L pylon add over 1,000 lbs.