F-35 Joint Strike Fighter News, Videos and pics Thread

[Jura The idiot]

Re: F-35 Joint Strike Fighter Thread

On F-35 CAS:

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[Jura The idiot]

Re: F-35 Joint Strike Fighter Thread

Guys the tanks don't have to be painted white, the media is sensationalizing this issue.

...

this might be the case, and now the CNBS like softened the story:

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but at the same time you may check this:

According to experts:

What matters for SGR is that when an aircraft lands, it is hot and hot all over. The gun system and the bullets are designed as a heat sink. General Dynamics has fully tested the gun system and PGU-23 TP in that environment, but not the planned combat round (PGU-20 DU).

As a result, when the jet lands on a hot day, the aircraft is hot. Putting fuel into it will immediately cool it off. However, no one knows what will happen on the 2nd sortie of the day. Is the aircraft able to cool off back to the point it was when it started its systems up at the beginning of the day?

Airflow through the aircraft does not cool the aircraft so when electronic systems generate heat, the thermal management system has to find a way to remove that heat so as not to melt the internal components. The main method for doing this on the F-22 and F-35 is using PAO (Polyalphaolefin), a flammable liquid.

PAO lines runs throughout the systems and absorbs heat from the electrical components. The PAO lines then run through the fuel cells and release heat into the fuel. For the aircrafts’ engines this increases their performance by preheating the fuel while fixing the cooling issue for the aircraft. What becomes an issue is when it is hot outside and the engine is running at low power (before takeoff). It is also a problem when running the engine at high power because the engine becomes a heat generator at that point. To solve this problem, the aircraft profile for the F-35 is to climb to 30,000′, cool the aircraft down for a while, then execute the mission profile.

Once the plane gets extremely hot in the air, the only solution is to turn off components like the radar. If the aircraft will have serious problems most likely if it is at low altitude for a long period of time in high power settings.

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[Pointblank]

Re: F-35 Joint Strike Fighter Thread

Guys the tanks don't have to be painted white, the media is sensationalizing this issue.

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Also I'm pretty sure the issue is due to the bravo units V/STOL requirements, not avionics. Would be nice to find out the reason for the temperature threshold.

-Greg

Also, consider fuel temperature thresholds. The F/A-18 NATOPS indicates that any time ambient air temperature is above 85F using JP-4 fuel idle power decelerations between Mach 1.23 and Mach 0.9 may result in an engine flameout. Furthermore extended low altitude flights with less than 4,000 pounds fuel remaining could result in the Airframe Mounted Accessory Drive (AMAD) to overheat, thus the pilot is required to monitor fuel temperatures, and if the fuel temperature exceeds 75C, the pilot is to land ASAP.

In addition, the NATOPS indicates the following as well:

During ground operation after flight, an AMAD caution may occur due to the lack of ram air cooling and low fuel state. Below 1,000 pounds fuel remaining and above 30°C, an AMAD caution will appear almost immediately. Above 3,000 pounds of fuel remaining and below 30°C, an AMAD caution should not occur. Between these conditions, the time before an AMAD caution will appear is a function of fuel state and ambient temperature (15 minutes at 24°C and 2,000 pounds fuel). Lower fuel quantities and higher ambient temperatures will reduce the time before an AMAD caution will appear. Shutting down an engine (left engine shutdown preferred) will extend the ground operating time. If the AMAD caution appears, shut down the associated engine.

There is a section as well regarding hot weather procedures, and the NATOPS indicates that if you are flying an F/A-18 Hornet, you need to shut all non-essential electronic equipment (radar, tacan, IFF, etc.) during ground operations until just prior to takeoff. The document also says that one is recommended to increasing the throttle setting above idle power or at ground idle, using the APU in AUG pull mode to supply bleed air to the ECS if external temperatures exceed 103F.

 

[Jura The idiot]

Re: F-35 Joint Strike Fighter Thread

Also, consider fuel temperature thresholds. The F/A-18 NATOPS indicates ...

do you have F-35 NATOPS?

 

[thunderchief]

Re: F-35 Joint Strike Fighter Thread

This is a very serious matter if true. Can you provide citation? If the F35 is basically useless at say less than 10 or 20% remaining fuel load we would have a lemon on our hands. Even if say 80% has more than adequate range we're still talking significant overhead in terms of weight and performance penalties.

No, I can't , at least not now. But you could make your own conclusion - fuel used as heat sink, no fuel means ....

I think you boys need to take a "chill pill", if you've ever been around JP, it is a light, very light and highly refined light oil, basically kerosene. As you heat it, it becomes much less dense, and with far less ability to absorb heat, in extreme arctic conditions it must be preheated in order to burn properly, without treatment, it will "grow" things and gum up your injectors... and really guys, I mean really, they are painting the fuel trucks with reflective paint to keep the sunlight from being absorbed by the steel tanks of the fuel truck... I know none of you have ever owned a black car??? right, ask Jeff Head, he lived in Texas?

Problem lies in that tiny little term "ability to absorb heat" Other planes do not need that ability , they are happily flying with warm fuel from green trucks . F-35 cannot because it needs "ability to absorb heat" . Ok, you could cool down fuel for F-35 . But what happens when fuel nearly runs out ? There is no "ability to absorb heat" then .

 

[TerraN_EmpirE]

Re: F-35 Joint Strike Fighter Thread

No, I can't , at least not now. But you could make your own conclusion - fuel used as heat sink, no fuel means ....



Problem lies in that tiny little term "ability to absorb heat" Other planes do not need that ability , they are happily flying with warm fuel from green trucks . F-35 cannot because it needs "ability to absorb heat" . Ok, you could cool down fuel for F-35 . But what happens when fuel nearly runs out ? There is no "ability to absorb heat" then .

I am surprised you have not tried to bring up the fueldraulic lines well your at it.
At altitude the air temperature drops the air it's self cools. but if your going to go through this might i point out that if you have no fuel in you F35 or any jet for that matter Heating is the least of your worries.

 

[thunderchief]

Re: F-35 Joint Strike Fighter Thread

but if your going to go through this might i point out that if you have no fuel in you F35 or any jet for that matter Heating is the least of your worries.

We were talking about situations with low fuel ( 30% and lower ) , not about no fuel at all .

 

[Jura The idiot]

Re: F-35 Joint Strike Fighter Thread

some debater under some of the most recent articles on "F-35 cooling" asked (I lost the track) an interesting question: how long does it take an F-35 to cool off, in the sense once it comes back from a sortie on a hot day, when can it be sent again? (the answer could be for example "immediately after refueling"; "after six hours"; "only the next day") ... any thoughts?

 

[TerraN_EmpirE]

Re: F-35 Joint Strike Fighter Thread

at 30% or lower the pilot is already looking for a place to land. Jet fighters are hardly fuel efficient. now your primary worry is the heat sink. since the jet is in the air already and flying she is under the effect of convection with low temperature air flowing in and around the fighter.

 

[Jura The idiot]

Re: F-35 Joint Strike Fighter Thread

at 30% or lower the pilot is already looking for a place to land. Jet fighters are hardly fuel efficient. now your primary worry is the heat sink. since the jet is in the air already and flying she is under the effect of convection with low temperature air flowing in and around the fighter.

TE, but the problem as I understand it (but probably I don't is the risk the pilot would have to turn off the radar when on low fuel ...