F-35A versus Saab Gripen NG

The F-35 compared with other modern jets.
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SpudmanWP

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Unread post08 Nov 2008, 20:35

I do not know if the fuel flows through the EHA. I do know that each EHA also has a backup. So, if the cooling loop, or other component of each EHA fails, it is backed up without affecting the whole system.

The EHAs will be cooled as long as you have fuel in the system. If they fail, the backups kick in.

If you are out of fuel, you have bigger problems than cooling the EHAs ;)
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einstein

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Unread post08 Nov 2008, 20:44

SpudmanWP wrote:Dude… Do you even know what Google is??? I have to wonder. A few minutes searching for info here, came up with plenty of info.

1. Here is the specific info on Parker’s (Actuator Contractor) EHA Spec for the F-35.
F-35 Fighter incorporates EHA. (Ideas & Applications).
Source: Hydraulics & Pneumatics
Publication Date: 01-DEC-02
The new Lockheed Martin F-35 Joint Strike Fighter's flight controls will use electrohydrostatic actuation (EHA) technology for the first time in a production aircraft. Parker Aerospace Control Systems Div.-Military and Moog, Inc. are jointly designing and developing the primary flight control actuation system The Parker/Moog team is also responsible for power drive electronics on all three variants of the F-35.

The EHA technology provides several benefits. The actuators are smaller and weigh slightly less; performance is more efficient, and the F-35 is less vulnerable to enemy fire.
The 4000-psi EHA actuators have flow capabilities up to 26 gpm, depending on the surface. There are two basic configurations: a simplex configuration (rudder and aileron) and the dual-tandem (horizontal tail and flapperon).

These sophisticated actuator packages contain the following:
* a ram assembly with triple-redundant rod seals to minimize leakage,
* an integral triplex-ram LVDT,
* a liquid-cooled DC motor with integral resolver,
* a bidirectional shoeless pump -- capable of speeds to 15,000 rpm,
* a metal-bellows reservoir with level sensing,
* pilot-actuated solenoid valves to control mode logic (one spool-in-sleeve logic valve for the simplex version, three for the dual-tandem version),
* anti-cavitation check valves,
* control-pressure relief valves,
* fill and bleed ports,
* control-port and reservoir pressure transducers, and
* motor-coil and reservoir temperature transducers.
Wow, look at that… it has liquid cooling and specifically addresses thermal issues. Who would have thought???

2. Parker has stated
Electrohydrostatic actuation (EHA) is a power-by-wire system that eliminates the need for central hydraulics. EHAs are self-contained hydraulic systems controlled by high power electronics, allowing the use of traditional proven hydraulic actuation configurations for fault tolerance. Parker EHAs provide reduced system weight, reduced power consumption, and improved maintainability.

We have taken a leadership role with our system of EHAs, used to power all primary flight control surfaces on the F-35 Joint Strike Fighter. Jointly developed with our teammates Moog and Hamilton Sundstrand, EHAs contribute significantly to performance improvements and weight reduction at the aircraft system level.


Just to be fair and balanced ;) here is the article that describes the serious problem they had in 2006. In it, they describe the issue as an electrical (lead shorted on lid) issue and specifically state that the EHAs were not an issue.

Oh and just to stick a fork in you, AWST did an article in August specifically addressing the heat issues and the presence of a central "massive fuel/air heat exchanger”.


No news for me and you miss the point all the time: The very basic 20% heat loss when running the motor and pump without an external cooling circuit is acceptable in an airliner but not in a fighter
Liquid cooling in spec above means that the motor is installed wet in fluid inside the package

Have to give up on you ´´Google´´

To point that out, you are impressed by all the sensors in the package:
X-32 Boeing man said, sensors are the most sensitive components in a hydraulic system.
With F-35 10 packages, all with sensors, compared to the conventional X-35 system, then you decrease reliability with a very high factor
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Raptor_claw

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Unread post08 Nov 2008, 22:26

einstein wrote:You are right, that I don´t know how LM is handling this problem, but suppose it´s done like in B-787 with EHA´s, you fly like an airliner
So, why would you suppose it's done like a 787???? You are basically saying you don't think LM understands control surface usage for a fighter. That would be based on what, exactly? :bang:
The simple fact is that the kinds of events (radical things like landings, air refueling, close formation) where the heat buildup is most critical have been done (repeatedly) and the aircraft didn't melt.
einstein wrote:...for F-35 and for which - USAF had demanded - EHA´s
Not true.
einstein wrote:The Boeing man said they had refused to do that in a fighter and he had a lot of more reasons not to do that, but it gets too hydraulic,
And when was the last time Boeing produced a successful fighter? (And no, the F-15 and F-18 do NOT count).
einstein wrote: my point is that you basically can´t be a fighter with hot and slow EHA´s
Which is why you design the system so that it's not slow and doesn't get too hot. Seems like it wouldn't take an Einstein to understand that.
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Raptor_claw

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Unread post08 Nov 2008, 22:45

SpudmanWP wrote:
Casey wrote: His job to the public is----MARKETING! Citing LM's marketing people as a credible source?
No, his job is an USAF officer and pilot. He does not work for LM. Are you saying that all USAF personnel that have worked on the F-35 cannot be trusted? Then how do we trust your un-named and un-quotable USAF personnel?

Just keeping the record straight, Jon is an LM employee and has been since the late 80's. He retired from USAF following a very distinquished career, including developmental testing for the F-117.
But, back to Casey's insane statement. To somehow suggest that Jon would sacrifice even a fraction of his personal ethics and professional standards in the interest of "marketing" is, at best, just ignorant. Jon's job (and the job of all the other pilots involved at this point (and that includes former F-16, F-18, F-15, AV-8A, AV-8B, F-14 pilots, by the way)) is to provide the very best possible platform for future generations of pilots - period. To imply otherwise is criminal.
If you would rather put your faith in accusations from uncredited "sources", who have no direct insight into the program, and have personal grudges and/or political axes to grind, well go ahead - I can't stop ya.
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dwightlooi

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Unread post09 Nov 2008, 00:05

Well... there are always going to be accusations of this sort.

Worse yet, I recall a comment a couple of months back along the lines that the very fact that Jon Beesley is the chief test pilot proves that the F-35 flies like a 737 because otherwise they will need a real fighter jock in his prime (say 30 years old) rather than the nearly 60 year Jon. Whoever it was (I forgot) then went on to say that Jon has been nursing the AA-1 never ever pulling G-max turns right of the ground or charging it past Mach 1 because he probably knows it can't handle either.
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Corsair1963

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Unread post09 Nov 2008, 00:12

dwightlooi wrote:Well... there are always going to be accusations of this sort.

Worse yet, I recall a comment a couple of months back along the lines that the very fact that Jon Beesley is the chief test pilot proves that the F-35 flies like a 737 because otherwise they will need a real fighter jock in his prime (say 30 years old) rather than the nearly 60 year Jon. Whoever it was (I forgot) then went on to say that Jon has been nursing the AA-1 never ever pulling G-max turns right of the ground or charging it past Mach 1 because he probably knows it can't handle either.



Typical........... :?
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Conan

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Unread post09 Nov 2008, 06:11

Casey wrote:
SpudmanWP wrote:rapier01 just posted a link to a great interview with the first pilot of the F-35..if you [wink]choose[/wink] to believe him.


His job to the public is----MARKETING! Citing LM's marketing people as a credible source?


His job is to fly F-35 AA-1 and F-35 BF-1. He was the first person to fly the first "production representative" (pre-SWAT) and one of the first to fly the first "weight optimised" F-35.

He is limited in what he can say publicly about the aircraft because it IS classified information that people want. He has discussed the flight characteristics of BOTH aircraft at length, as far as the testing has gone so far. With 3-4 more airframes due to be flying within the next 12 months, the flight testing WILL ramp up considerably and a lot more information will be released.

It is not his job to sell the aircraft.

It is a VERY interesting situation amongst critics of the F-35. They almost uniformly love the F-22 (made by Lockheed Martin) and believe the world of that aircraft and everything ever said about it, but believe NOTHING said about the F-35...

Jon Beesley was involved in the development program of both aircraft. He was apparently entirely trustworthy and believable about the F-22, but now he is simply an L-M shrill and nothing from his mouth can be believed?

Makes me wonder if the issue is really with him...
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Unread post09 Nov 2008, 16:14

Spudman: You can cool an electric motor with JP if you like. Just warn me so I can stay 100 yards away.

Although EHA tested out on the J/IST. it wouldn't be the first time that a technology looked like a good deal at one end of a program, and not so good at the other. And there is a lot of legitimate concern about thermal loading on the F-35.
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Unread post09 Nov 2008, 18:05

Raptor_claw wrote:
SpudmanWP wrote:
Casey wrote: His job to the public is----MARKETING! Citing LM's marketing people as a credible source?
No, his job is an USAF officer and pilot. He does not work for LM. Are you saying that all USAF personnel that have worked on the F-35 cannot be trusted? Then how do we trust your un-named and un-quotable USAF personnel?

Just keeping the record straight, Jon is an LM employee and has been since the late 80's. He retired from USAF following a very distinquished career, including developmental testing for the F-117. ....


Sorry, I got my notes crossed... I was busy packing for a weekend camping trip.

However, THIS REPOT and THIS ONE is from the first USAF pilot to fly the F-35. He flew AA-1 in early 2008. His name is Lt. Col. James “Flipper” Kromberg.

Also, he is not just some fighter jock, he is the director of operations for the 461st Flight Test Squadron.

In short, he was very impressed.
"The aircraft flew very well, exceeding my expectations," Kromberg said. "I was surprised by the amount of power on the takeoff roll. And the handling, particularly with the gear up, was phenomenal. The aircraft was very stable flying in formation with another airplane. It was really a joy to fly."
After the flight, Colonel Kromberg said the F-35 flew "very well."

"The aircraft was responsive across all flight regimes," Colonel Kromberg said. "The engine thrust response was excellent -- accelerating very quickly. The aircraft was very stable during formation flight."
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sferrin

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Unread post09 Nov 2008, 18:15

LowObservable wrote:Spudman: You can cool an electric motor with JP if you like. Just warn me so I can stay 100 yards away.


I'm pretty sure they're not running bare wires through the fuel. :wink:
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Unread post09 Nov 2008, 18:57

LowObservable wrote:Spudman: You can cool an electric motor with JP if you like. Just warn me so I can stay 100 yards away.

Although EHA tested out on the J/IST. it wouldn't be the first time that a technology looked like a good deal at one end of a program, and not so good at the other. And there is a lot of legitimate concern about thermal loading on the F-35.
The EHAs on the F-35 have been in development since before 1996. That's 13 years ago. I would think that they have all the thermal and flight characteristics issues resolved.

btw, they have been using fuel-cooling of aircraft systems for years.
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Unread post09 Nov 2008, 22:16

Couple of people here probably need to do some more research on what engineers do with electrical components and fuel.

LO, if you think you want to stay away from fuel cooled components then you'll need to stay away from more than the JSF. You'll need to stay away from your car (if its a GM), away from Boeings and Airbus products and... a whole host of other useful modes of transportation.

I just replaced my fuel pump out of my truck and you'll never guess where it was located...inside the gas tank. I'm sure everyone here knows that automobile gas flash point is much lower than JP8's, so it would make less sense to put an electric motor in an automobile's gas tank if it isn't safe for an airplane. (Very simplistic anecdote, I know, but I was surprised that I had to crack open my car's fuel tank to get to the fuel pump module.)

I'm pretty sure fuel cooling works on electrical components.
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Unread post09 Nov 2008, 22:36

einstein wrote:No news for me and you miss the point all the time: The very basic 20% heat loss when running the motor and pump without an external cooling circuit is acceptable in an airliner but not in a fighter
Liquid cooling in spec above means that the motor is installed wet in fluid inside the package

Have to give up on you ´´Google´´

To point that out, you are impressed by all the sensors in the package:
X-32 Boeing man said, sensors are the most sensitive components in a hydraulic system.
With F-35 10 packages, all with sensors, compared to the conventional X-35 system, then you decrease reliability with a very high factor
You throw around that 20% number like it is a constant and never improves. Got ANY sources to back that up? No, thought not.

I however, have a few sources you might like to look at. THIS press release speaks about NASA’s flight tests of EHA and EMA actuators in the F-18 test aircraft. Both of the links are PDF reports of the results from these tests. Btw, LM designed the EHA actuator for the test.

Here are some of the highlights.
1. Both the EHA and EMA performed identically to the legacy central-hydraulic system.
2. Either system is more reliable than legacy systems
3. Either system saves about 1000lbs from the design of an aircraft
4. The EHA was designed to require no Actively Cooling.
5. And here is the big one (re:EMA testing)…. Wait for it… Wait for it…
The most significant problem uncovered during this flight test program was actuator thermal performance. This had more to do with underestimating the aircraft aileron duty cycle during the early part of the design phase than with any inherent limitations in EMA technology. The worst-case thermal loading condition was assumed to occur during hard, tactical maneuvering. In reality, the worst case occurs when the aircraft deploys the ailerons as flaps, flying around for extended periods of time with the ailerons drooped from 30 to 45 degrees. This extended operation against a steady load, coupled with the continuous small corrections commanded by the flight control system at these slow speeds, twice caused the test team to terminate a test point, raise the flaps, and allow the actuator to cool (Figure 15). MPC fabricated heat sinks for the motors to increase the conductive path to the actuator body. These were retrofitted onto the actuator midway through the flight program. This modification significantly improved actuator thermal performance.


So, we can derive two things from that statement:
1. The EMAs generated, and built up, more heat than the EHAs. This is probably why the F-35 was designed with EHAs instead of EMAs.

2. You are COMPLETELY wrong in your assertion that “F-35… can´t be a fighter with hot and slow EHA´s” as they don't get hot and are not slow.
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sferrin

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Unread post09 Nov 2008, 22:53

F16guy wrote:Couple of people here probably need to do some more research on what engineers do with electrical components and fuel.

LO, if you think you want to stay away from fuel cooled components then you'll need to stay away from more than the JSF. You'll need to stay away from your car (if its a GM), away from Boeings and Airbus products and... a whole host of other useful modes of transportation.

I just replaced my fuel pump out of my truck and you'll never guess where it was located...inside the gas tank. I'm sure everyone here knows that automobile gas flash point is much lower than JP8's, so it would make less sense to put an electric motor in an automobile's gas tank if it isn't safe for an airplane. (Very simplistic anecdote, I know, but I was surprised that I had to crack open my car's fuel tank to get to the fuel pump module.)

I'm pretty sure fuel cooling works on electrical components.


Did the same thing on an '86 Chrysler Laser back in the day so it's not like it's a new thing even. (I'll admit my first thought was "WTF? Why don't they just make it so I have to pull the engine while I'm at it?")
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F16guy

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Unread post10 Nov 2008, 03:32

sferrin,
I was about to try that as looked for the damn thing then called in people way more knowledgeable and had to say no s#!t, as they told me where the pump was.

One thing I can count on is for SpudmanWP to do the research to be able to jump from the top rope and lay the smack down.
SpudmanWP, by the way, did you get my PM?

Let the games continue....
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