Where are you getting the factor of two from? The amount will depend on how much airflow they are planning to divert with the third stream and at what pressure. I don't know if either has been decided yet.
By: TomcatViP
- 10th August 2019 at 20:53Permalink
Let's say that we have initially a diameter of 1
Add 0.1 at each diametral extremities (the thickness of the added stream) and the new diameter become 1+ 2x0.1 ;)
By: halloweene
- 15th August 2019 at 07:20Permalink
Let's say that we have initially a diameter of 1
Add 0.1 at each diametral extremities (the thickness of the added stream) and the new diameter become 1+ 2x0.1 ;)
Air intakes are desined for the enhanced air flow? (genuine question)
By: XB-70
- 15th August 2019 at 12:57Permalink- Edited 15th August 2019 at 13:01
[USER="41059"]halloweene[/USER] - The airflow in the intakes doesn't appreciably change. You could change it, if there is opportunities for further enhancement and internal tolerances within the structure of the plane and such support it. But it doesn't have to. Having the third stream just changes bypass airflow.
[USER="39911"]TomcatViP[/USER] - That doesn't get you a reduction of a factor of two but I'll take that as a good initial approx.. They will probably reduce the internal volume of the engine core (to get their high pressure ratio) by a slight amount though - like how I first proposed - instead of bumping up the external diameter of the engine (and intake). So, since pressure is a factor it could be slightly more than that. We're talking small changes though...no need for the drastic difference in the size between the fan and the core seen in airliners because that third stream is compressed and so gives a very high bypass flow. And that means the engine will be very efficient because the fan can run at its optimum speed simultaneously with the LP and HP spools - which cannot happen with the big airliner engines without coupling the fan through reduction gears.
By: TomcatViP
- 15th August 2019 at 15:55Permalink- Edited 15th August 2019 at 16:01
We are looking at a safe margin of +- 9t of ordinance to implement any modification...
Also, third stream will generate power that could be used on cooling (beyond their inherent participation to insuling the hot section) leaving the extra amount of fuel that has to be kept for that to a bare minimum. This will open op birds to some weight savings, opening room for the new propulsion system.
By: djcross
- 15th August 2019 at 17:51Permalink- Edited 15th August 2019 at 17:52
Another genuine question : won't a triple flow enhance too much the engine weight? Apparently weight tolerances are quite low on F-35
There are several parameters which are key contributors of an airplane's predefined performance baseline (aerodynamics, propulsion and mission profile are the contributors with greatest impact). Weight affects aerodynamics by requiring more angle of attack to provide lift as weight increases. And increased angle of attack drives induced drag which negatively impacts range, speed and acceleration (typical performance baseline requirements). Designers use the weight growth curve to assure weight stays under control and the performance baseline is achieved, all other key contributors remaining constant. "All other key contributors remaining constant" is the catch. Adding 3rd stream propulsion performance is not constant with respect to current F135 performance. This allows the design team to re-balance the design to achieve the airplane's predefined performance. Improved propulsion performance may offset the weight increase. If a great benefit to airplane's performance can be achieved, the predefined performance goals will likely be altered, e.g. combat radius increase.
By: TomcatViP
- 15th August 2019 at 17:59Permalink- Edited 15th August 2019 at 18:00
What are we looking at for 3rd stream, 250kg?
It's marginal. Think also that the reduced core section will generate more weight savings than the increase brings in. We might end with an even result ;)
What are we looking at for 3rd stream, 250kg?
It's marginal. Think also that the reduced core section will generate more weight savings than the increase brings in. We might end with an even result ;)
That definitely could happen. The third stream is relatively low temp. You could build the necessary structure out of CFRP. The core section is where your dense nickel based alloys are. Even small reductions there counts for a lot with regards to weight.
Advanced EOTS is Multi-Spectral and due to it's "plug-n-Play design (with current F-35s), any image processing would be done in the unit itself.
Lockheed Martin (NYSE: LMT) has continued development of its Advanced Electro-Optical Targeting System (EOTS), which offers crystal clear resolution, unmatched multi-spectral range and significant cost savings for the F-35 Lightning II.
Advanced EOTS includes a larger aperture and provides pilots with multi-spectral sensing options such as high-resolution Mid-Wave IR, Short-Wave IR and Near IR. Utilizing the same volume and weight, Advanced EOTS is effortless to integrate into the F-35 Lightning II with the "plug and play" feature.
Posts: 5,905
By: TomcatViP - 10th August 2019 at 17:06 Permalink - Edited 10th August 2019 at 17:09
Another thing smaller and gigantic:
The Bee just got a queen
Posts: 333
By: XB-70 - 10th August 2019 at 17:21 Permalink
Where are you getting the factor of two from? The amount will depend on how much airflow they are planning to divert with the third stream and at what pressure. I don't know if either has been decided yet.
Posts: 5,905
By: TomcatViP - 10th August 2019 at 20:53 Permalink
Let's say that we have initially a diameter of 1
Add 0.1 at each diametral extremities (the thickness of the added stream) and the new diameter become 1+ 2x0.1 ;)
Posts: 4,168
By: halloweene - 15th August 2019 at 07:16 Permalink
Anther legal issue for helmet...
https://patentdocs.typepad.com/files/order-17.pdf
Posts: 4,168
By: halloweene - 15th August 2019 at 07:20 Permalink
Air intakes are desined for the enhanced air flow? (genuine question)
Posts: 333
By: XB-70 - 15th August 2019 at 12:57 Permalink - Edited 15th August 2019 at 13:01
[USER="41059"]halloweene[/USER] - The airflow in the intakes doesn't appreciably change. You could change it, if there is opportunities for further enhancement and internal tolerances within the structure of the plane and such support it. But it doesn't have to. Having the third stream just changes bypass airflow.
[USER="39911"]TomcatViP[/USER] - That doesn't get you a reduction of a factor of two but I'll take that as a good initial approx.. They will probably reduce the internal volume of the engine core (to get their high pressure ratio) by a slight amount though - like how I first proposed - instead of bumping up the external diameter of the engine (and intake). So, since pressure is a factor it could be slightly more than that. We're talking small changes though...no need for the drastic difference in the size between the fan and the core seen in airliners because that third stream is compressed and so gives a very high bypass flow. And that means the engine will be very efficient because the fan can run at its optimum speed simultaneously with the LP and HP spools - which cannot happen with the big airliner engines without coupling the fan through reduction gears.
Posts: 4,168
By: halloweene - 15th August 2019 at 13:05 Permalink
Another genuine question : won't a triple flow enhance too much the engine weight? Apparently weight tolerances are quite low on F-35
Posts: 5,905
By: TomcatViP - 15th August 2019 at 15:55 Permalink - Edited 15th August 2019 at 16:01
We are looking at a safe margin of +- 9t of ordinance to implement any modification...
Also, third stream will generate power that could be used on cooling (beyond their inherent participation to insuling the hot section) leaving the extra amount of fuel that has to be kept for that to a bare minimum. This will open op birds to some weight savings, opening room for the new propulsion system.
Posts: 5,396
By: djcross - 15th August 2019 at 17:51 Permalink - Edited 15th August 2019 at 17:52
There are several parameters which are key contributors of an airplane's predefined performance baseline (aerodynamics, propulsion and mission profile are the contributors with greatest impact). Weight affects aerodynamics by requiring more angle of attack to provide lift as weight increases. And increased angle of attack drives induced drag which negatively impacts range, speed and acceleration (typical performance baseline requirements). Designers use the weight growth curve to assure weight stays under control and the performance baseline is achieved, all other key contributors remaining constant. "All other key contributors remaining constant" is the catch. Adding 3rd stream propulsion performance is not constant with respect to current F135 performance. This allows the design team to re-balance the design to achieve the airplane's predefined performance. Improved propulsion performance may offset the weight increase. If a great benefit to airplane's performance can be achieved, the predefined performance goals will likely be altered, e.g. combat radius increase.
Posts: 5,905
By: TomcatViP - 15th August 2019 at 17:59 Permalink - Edited 15th August 2019 at 18:00
What are we looking at for 3rd stream, 250kg?
It's marginal. Think also that the reduced core section will generate more weight savings than the increase brings in. We might end with an even result ;)
Posts: 333
By: XB-70 - 15th August 2019 at 18:10 Permalink
That definitely could happen. The third stream is relatively low temp. You could build the necessary structure out of CFRP. The core section is where your dense nickel based alloys are. Even small reductions there counts for a lot with regards to weight.
Posts: 999
By: moon_light - 20th August 2019 at 11:43 Permalink
what is the tolerances?
Posts: 11,742
By: Sens - 30th August 2019 at 11:33 Permalink
https://www.slideshare.net/PraveenPratapSingh2/variable-cycle-engine-ppt-65048391
See 9/34 about that.
Posts: 484
By: LMFS - 31st August 2019 at 10:55 Permalink
Great read, thanks! This is going to become a crucial matter over the next years, for sure :eagerness:
Posts: 5,396
By: djcross - 19th September 2019 at 23:18 Permalink
First Two Vermont Air Guard F-35s Arrive at Burlington Airport
Posts: 5,197
By: SpudmanWP - 20th September 2019 at 03:30 Permalink
F-35 Advanced EOTS comparison.
[ATTACH=JSON]{"data-align":"none","data-size":"full","title":"2019-09-19 19_27_42-Window.png","data-attachmentid":3874130}[/ATTACH]
Advanced EOTS is Multi-Spectral and due to it's "plug-n-Play design (with current F-35s), any image processing would be done in the unit itself.
https://news.lockheedmartin.com/2019-09-17-Lockheed-Martin-Continues-Advanced-EOTS-Development
Maybe it's a QWIP sensor?
Posts: 156
By: RALL - 20th September 2019 at 18:49 Permalink
Wow, it seems a tv image. Really impresive performance.
Posts: 5,905
By: TomcatViP - 21st September 2019 at 09:40 Permalink - Edited 21st September 2019 at 09:41
Impressive and funny (notice how both seating chairs on the balconies are gone in the 2nd image).
Posts: 2,814
By: Levsha - 22nd September 2019 at 10:31 Permalink
The two different images may not have been taken at the same time or even on the same day.
Posts: 5,396
By: djcross - 14th October 2019 at 03:49 Permalink - Edited 14th October 2019 at 06:26
F-35 sea trials aboard the QE
https://www.dailymail.co.uk/news/article-7568983/F-35-Lightning-jets-HMS-Queen-Elizabeth-operational-trials.html