All-New Freewing PJ50 Twin 70mm EDF Jet - Official Thread

[avanti127]

Details of the testing are unknown, but I'm glad to hear that.

However, the points of my post were #1, FACT: I had an ESC stop working/shut down during a hot day ground run w/o any cooling air flow (stupid of me). and #2 FACT: Any electronics will last longer if you take care to keep the operating temperature down.

What I can state is that making a lot of flights on hot days with very little down time between flights AND all this flying has been done with cooling the ESC with the external PC case fan while the battery is being changed has given me good results (i.e., no more ESC failures). I prefer to have the maximum amount of margin possible.

Bottom line, if you're gonna get the PJ50 AND you fly in hot climates AND you do a lot of flights with little cool-down time between flights....you have another data point to reference.

-GG

I agree on the down times. I always wait between flights anyway that's why I take at least two bird with me to the field.

[Twowingtj]

avanti127 That's pretty sweet.

[avanti127]

I am going with the classy look.

[GliderGuy]

No different than the AL37 ESC location and never had an issue. Plus they said it was tested for almost year in hot climates.

Details of the testing are unknown, but I'm glad to hear that.

However, the points of my post were #1, FACT: I had an ESC stop working/shut down during a hot day ground run w/o any cooling air flow (stupid of me). and #2 FACT: Any electronics will last longer if you take care to keep the operating temperature down.

What I can state is that making a lot of flights on hot days with very little down time between flights AND all this flying has been done with cooling the ESC with the external PC case fan while the battery is being changed has given me good results (i.e., no more ESC failures). I prefer to have the maximum amount of margin possible.

Bottom line, if you're gonna get the PJ50 AND you fly in hot climates AND you do a lot of flights with little cool-down time between flights....you have another data point to reference.

-GG

[avanti127]

Something to consider (possibly overkill depending upon your flying style and typical flying air temperatures)...

(Photo below) I see that the ESCs are mounted in the rear tail cone. Thus, as with the AL37, cooling air only flows over them when the jet is in motion.

This design leads to a few things which you may be getting prepared for....as learned from my AL37 (summertime days get HOT here)::

1. Running down the batteries while stationary isn't a good idea. The ESCs get hot and heat is problematic for electronics. They'll last longer if you keep them cooler.
2. If you must run down the batteries while on the ground, get some cooling air flowing into the ESC compartment.
3. I built a cooling fan from a high volume/rpm, 24-volt DC PC case fan attached to one end of an old 6S battery and added a switch.
4. The AL37 sits low enough so I place this cooling fan+battery assembly on the ground under the AL37 and blow air up onto the ESCs.
5. Since typically I strive for a short down time between flights...as soon as the AL37 lands and taxis back, I put the cooling fan assembly under the bird and begin blowing air over the ESCs while I change the battery.

I see that the PJ50 ESC compartment is high up and located on the underside of the tail cone. This will require building a small shelf for the fan+battery assembly to get the assembly high enough off the ground to effectively blow cooling air into the ESC compartment.

Alternatively, when the bird arrives, I am going to evaluate this area and determine whether or not there is sufficient room to mount a small cooling fan in there that will be circulating air any time the main battery is connected. DC fans don't draw much current at all.

Overkill....possibly. But electronics are happier when they are cooler. And, I have had an ESC shut down on me due to overheating while running down batteries on the ground when I could not fly off the charge.

-GG

Screen capture from the announcement video...

No different than the AL37 ESC location and never had an issue. Plus they said it was tested for almost year in hot climates.

[avanti127]

This thing is going to be a rocket and will sell like hotcakes. I think they've read the room brilliantly. Great job guys.

There's a decade long back catalogue of military EDFs for people to work through.

As for pricing, I heard the US is nudging 7% inflation? And you're gonna benchmark price against planes released years ago? Come on.

I agree with you. The market is pretty saturated with Military aircraft and it's about time we get civilian jets into the mix.

[Evan D]

Yes, the "other" contender...

[Bajora]

[GliderGuy]

People actually do that? I can see doing it momentarily for watt and amp measurements but just running it to drain the batteries down? I just take them home and put them on the dis-charger OR drive them up and down the runway a couple of times.

Ummm….Yes.

Consider 4 min of runtime on the ground at cruise power vs sometimes hours on a discharger vs who knows how many trips up and down a runway at taxi power (a lot of taxing…more than a few trips) to use 60% to 70% of a 6000 mAh cell and reach the recommended 3.8 V storage voltage. Assuming a 10 amp draw at taxi power = almost half an hour of taxi trips (just a guess = 10 A). And I have 10 batteries to discharge if the weather turns bad.

I’ve done it and learned it isn’t a good idea when the ESC shut down. If I do it now, I supply cooling airflow to the ESCs on birds that don’t have the ESC mounted in the engine airflow stream or propwash stream.

Call it….Lessons learned and passed along for the edification of others.

Best way….Use the MiG-29!!! 2 batteries at a time and ESCs mounted in the fan’s airflow stream. 10 batteries discharged in 20 min without any ESC overheating concerns.

-GG

[xviper]

1. Running down the batteries while stationary isn't a good idea. The ESCs get hot and heat is problematic for electronics. They'll last longer if you keep them cooler.

People actually do that? I can see doing it momentarily for watt and amp measurements but just running it to drain the batteries down? I just take them home and put them on the dis-charger OR drive them up and down the runway a couple of times.

[GliderGuy]

So if the AL-37 is a Boeing 737 Max, (nod, nod, wink, wink), what is the PJ-50?
Cessna? Lear?

A close match…

[Gilatrout]

So if the AL-37 is a Boeing 737 Max, (nod, nod, wink, wink), what is the PJ-50?
Cessna? Lear?

Gulfstream

[ridgerunner]

So if the AL-37 is a Boeing 737 Max, (nod, nod, wink, wink), what is the PJ-50?
Cessna? Lear?

[GliderGuy]

Something to consider (possibly overkill depending upon your flying style and typical flying air temperatures)...

(Photo below) I see that the ESCs are mounted in the rear tail cone. Thus, as with the AL37, cooling air only flows over them when the jet is in motion.

This design leads to a few things which you may be getting prepared for....as learned from my AL37 (summertime days get HOT here)::

1. Running down the batteries while stationary isn't a good idea. The ESCs get hot and heat is problematic for electronics. They'll last longer if you keep them cooler.
2. If you must run down the batteries while on the ground, get some cooling air flowing into the ESC compartment.
3. I built a cooling fan from a high volume/rpm, 24-volt DC PC case fan attached to one end of an old 6S battery and added a switch.
4. The AL37 sits low enough so I place this cooling fan+battery assembly on the ground under the AL37 and blow air up onto the ESCs.
5. Since typically I strive for a short down time between flights...as soon as the AL37 lands and taxis back, I put the cooling fan assembly under the bird and begin blowing air over the ESCs while I change the battery.

I see that the PJ50 ESC compartment is high up and located on the underside of the tail cone. This will require building a small shelf for the fan+battery assembly to get the assembly high enough off the ground to effectively blow cooling air into the ESC compartment.

Alternatively, when the bird arrives, I am going to evaluate this area and determine whether or not there is sufficient room to mount a small cooling fan in there that will be circulating air any time the main battery is connected. DC fans don't draw much current at all.

Overkill....possibly. But electronics are happier when they are cooler. And, I have had an ESC shut down on me due to overheating while running down batteries on the ground when I could not fly off the charge.

-GG

Screen capture from the announcement video...

[BigJim]

I always harass James for new product news and was glad to jump on this one as soon as the pre-order hit the site. Thanks for hitting a wish list item for me! I will be painting mine as a C-37A... only wish I could find the tail number(s) stationed at Hickam 1998 - 2000. If not, I know 10065 or 60500 were there later.

[BigJim]

I've noticed a couple of potential issues in the videos. The first is that James seems to be carrying a ton of up trim on his elevators indicating that his CG and possibly the book CG is way too forward. The second issue is that in one of the slo-mo landings, it looks like there is some fuselage flex in the aft section.

Both are easy to solve. For the flexing issue, I'm going to add additional carbon fiber slats internally along the tail and up the fuselage to stiffen the area where the two pieces meet. As to the CG, Ill figure out if I need to do more than move the battery after I add the stiffeners.

March is soo far away....

Saw the aft section flex during landing as well. I wonder how many landings the tail can take before they start to fail. I hope to remember this in March... age ya know!

[Twowingtj]

When I looked at the manual, I was curios about the 5mm of up elevator. After looking at many images, including those above, there is usually a pronounced negative angle of attack in the horizontal stab.

This is such a sleek looking bird. It will be a welcome addition to the hangar.

[mshagg]

Im going to wring it out more this week now that the reveal is done. I was babying it with it being the only one. Just needed enough footage for the hype video. Definitely will try to get Major Croasdale on the sticks. He was there for the flight I showed (had a new baby, hadn't seen him in a bit). Hang tight.

But yes, Evan is right. The book calls for 5mm up, I did have to trim the elevator down on my maiden, but it was flying great for me so I didn't further play with it. I will now. Monday looks sunny and calm

Lol I assume it's considered poor form for the head of global marketing to put the demo model in!

[mshagg]

This thing is going to be a rocket and will sell like hotcakes. I think they've read the room brilliantly. Great job guys.

There's a decade long back catalogue of military EDFs for people to work through.

As for pricing, I heard the US is nudging 7% inflation? And you're gonna benchmark price against planes released years ago? Come on.

[Warbirdfan29]

I'm not usually into civilian aircraft, but I really like this model. Well done!
For me this model came as a surprise, I would have expected a Hawker Hunter, a F9F Panther or maybe even a T-7A red hawk.
In addition, there are countless variants of the "Gulfstream" that guarantee freedom for redesign and repainting.
In Germany, for example, there is the HALO research aircraft.
In other countries, the model is also used for military purposes. Think of the C-20 in the USA and the U-4 in Japan.