Has anyone built a 103 UL Hummel Ultracruiser?

[byGeorge]

To plans, or kit, how close to 254 is it (in other words do items have to be "left off" to get there)?
I assume you can't have a canopy due to it lowering the drag factor not the weight.
If you don't have a canopy does the turtledeck serve a purpose?
How long does it take to buff out all that aluminum?

 

[KeithO]

Since it doesnt look like a typical ultralight, Hummel must have expected extra scrutiny from the FAA, so as long as it is configured to meet the Part 103 requirements (see note above ) Im sure it will meet the requirements. I'm not certain but its also possible you might not be able to have brakes either. If you can comply with the sport pilot requirements, consider the H5. More room, more power, more speed, more endurance. No limitation on having the canopy or brakes and probably the same amount of effort to build.

 

[addicted2climbing]

I reached out to some ultracruiser builders and it does not make the stall speed requirement either. Between 25 and 26kts from those I got answers from. But then again, nobody is policing this and the regs say its on the builder not the designer to meet the rules.

 

[Dana]

the regs say its on the builder not the designer to meet the rules.

No, it's on the pilot to meet the rules.

 

[TFF]

The one that shows up at Oshkosh every year is the fastest UL in the pattern. As long as the winds are good, morning and evening are parades of ULs at the UL strip. Strings of them. He usually has to have the most room to not catch up to someone in front. It probably makes weight and has nothing extra. It’s definitely on the margins. Only he knows if it’s fully legal. It’s still slow.

 

[byGeorge]

I'd like having the additional speed and range of an X over a 103, but that conflicts with my desire to have as few dealings with the FAA as possible after having already paid to play following a ramp check where the inspector disagreed with the clear language in the type certificate:

"When empty weight C. G. falls within pertinent range, computation of critical fore and aft C. G. positions is unnecessary. Range is not valid for non-standard arrangements." (A-691)

Someone had to be made an example of to strike fear in everyone else. I was a student pilot and least likely to fight. It took them forever to admit their employee made a mistake. A properly documented, with a 337 and logbook entry, recover does not constitute a non-standard arrangement.

Neither speed needs to be demonstrated, so long as the aircraft as built doesn't exceed 55 and 24 knots per the worksheet:

"The use of the graphs provided in Appendixes 1 and 2 will be 6 acceptable for determlnatlon of the maximum level flight speed and power-off stall speed if your ultralight has no special limitations to maximum speed or power and no special high-lift-devices." (AC 103-7)

 

[TFF]

I know of multiple examples of crashes ULs that when the FAA showed up because it was called in as an airplane crash. They learn it’s a UL and they get back in their car and go to lunch. Unless you kill someone and you are calling your Cessna a UL, they are not going to give a flip. They don’t want to. They don’t want the report. They don’t want to have their name on a document. They don’t want to call the NTSB out to weigh all the parts.

You claim your plane a compliant PT103 vehicle, stick to it until they burry you. You are not supposed to be near anyone to hurt with one, so don’t. Just remember that the FAA won’t be the ones that catch you. You will find a Dudley Do Right who will complain you are breaking the rules a hundred times; to the point that they investigate you just to shut him up. If it goes 100, make sure there is no cameras, radar guns, stop watches where you fly. It’s not amazing to break the rules. It’s always amazing how many people want to show that off.

 

[Bigshu]

To plans, or kit, how close to 254 is it (in other words do items have to be "left off" to get there)?
I assume you can't have a canopy due to it lowering the drag factor not the weight.
If you don't have a canopy does the turtledeck serve a purpose?
How long does it take to buff out all that aluminum?

Dennis Brooks just finished another UC, and stated the dry weight at 245#. He's hoping to have a light enough canopy to install one. Lots of videos on you tube. I'm pretty sure the Hummel folks know their stuff on the weight, or else they wouldn't be able to claim its the only all metal legal ultra light. It's asking for trouble to base your whole sales approach on an easily disproved claim.

 

[Victor Bravo]

"When empty weight C. G. falls within pertinent range, computation of critical fore and aft C. G. positions is unnecessary. Range is not valid for non-standard arrangements." (A-691)

Someone had to be made an example of to strike fear in everyone else. I was a student pilot and least likely to fight. It took them forever to admit their employee made a mistake.

My Taylorcrafts (A-696) also had a similar situation, where if pilot and passenger together weighed less than X and more than Y the CG would automatically stay within range. Probably several other airplanes have something like this, especially the 2 seat side by side airplanes.

 

[Bigshu]

I reached out to some ultracruiser builders and it does not make the stall speed requirement either. Between 25 and 26kts from those I got answers from. But then again, nobody is policing this and the regs say its on the builder not the designer to meet the rules.

Hummel quotes 28mph stall, which is 24 knots. I think you have to be diligent about making weight to get the stall speed low. I'd consider VGs if I was worried about it.

 

[Victor Bravo]

You can remove all of the instruments AND any non-structural portion of the instrument panel. That will likely save several pounds from a "stock" airplane. All your flight instruments can be on your phone, which is in the pilot's pocket and not part of the empty weight. Although it would not make sense for anything other than meeting the letter of 103, you can remove the pitot tube and ten or fifteen feet of tubing that connects the pitot to the instruments, and all the Adel clamps and what-not that clamps the tube to the airframe, that's probably nearly a pound altogether. A thin welded aluminum tank, instead of a thicker plastic Jerry can can, will save a little bit if you are splitting hairs.

I highly recommend against it, but if you are wanting to demonstrate the legality of the aircraft, you can use slightly thinner webbing for the seat restraints, and sew the individual shoulder straps to the lap belt halves, getting rid of a pound of chrome steel buckles and such. The FAA guidelines for certified airplanes now indicate that the end of the bolt can be flush with the end of the self-lock nut... it used to be two threads, now it is zero. So shorter bolts that just meet this rule will save something, and then remember there are low-profile self-lock nuts that are physically smaller and probably weigh less. Being smaller, they allow a bolt that is even slightly shorter yet.

There are probably a lot of places whereyou can cut lightening holes OTHER than the main spar webs. I'm not that familiar with the Ultra Cruiser, but I'm sure thereare opportunities to add a little more fabrication time and get an ounce or two off of parts.

The point is that if you need to make weight, there are things you can do. Make no mistake, you will be paying for this in time, cost, or losing something that is nice to have (ASI).

I know that this will be seen as an absolute crime against all that is holy, but there are also lighter engines for the Ultracruiser than the VW derivatives. The 36HP Polini or perhaps others from Simonini and others, using a higher gear ratio and a larger diameter propeller, would give it plenty of low-end grunt.

Foam seat upholstery weight a couple of pounds, you might be able to use something lighter, an inflatable cushion instead of foam, upholstery weighs something, etc. etc.

 

[MACOWA]

You can remove all of the instruments AND any non-structural portion of the instrument panel. That will likely save several pounds from a "stock" airplane. All your flight instruments can be on your phone, which is in the pilot's pocket and not part of the empty weight. Although it would not make sense for anything other than meeting the letter of 103, you can remove the pitot tube and ten or fifteen feet of tubing that connects the pitot to the instruments, and all the Adel clamps and what-not that clamps the tube to the airframe, that's probably nearly a pound altogether. A thin welded aluminum tank, instead of a thicker plastic Jerry can can, will save a little bit if you are splitting hairs.

I highly recommend against it, but if you are wanting to demonstrate the legality of the aircraft, you can use slightly thinner webbing for the seat restraints, and sew the individual shoulder straps to the lap belt halves, getting rid of a pound of chrome steel buckles and such. The FAA guidelines for certified airplanes now indicate that the end of the bolt can be flush with the end of the self-lock nut... it used to be two threads, now it is zero. So shorter bolts that just meet this rule will save something, and then remember there are low-profile self-lock nuts that are physically smaller and probably weigh less. Being smaller, they allow a bolt that is even slightly shorter yet.

There are probably a lot of places whereyou can cut lightening holes OTHER than the main spar webs. I'm not that familiar with the Ultra Cruiser, but I'm sure thereare opportunities to add a little more fabrication time and get an ounce or two off of parts.

The point is that if you need to make weight, there are things you can do. Make no mistake, you will be paying for this in time, cost, or losing something that is nice to have (ASI).

I know that this will be seen as an absolute crime against all that is holy, but there are also lighter engines for the Ultracruiser than the VW derivatives. The 36HP Polini or perhaps others from Simonini and others, using a higher gear ratio and a larger diameter propeller, would give it plenty of low-end grunt.

Foam seat upholstery weight a couple of pounds, you might be able to use something lighter, an inflatable cushion instead of foam, upholstery weighs something, etc. etc.

MY Ultra cruiser kit arrived in March. It differs from the original blueprints one would use for a scratch building in some significant ways. If there is any place that a lightening hole can be used it's there ! The latest canopy kit weighs about 9 1/2 pounds. All fasteners are the lightest possible (I checked). I am installing a Rotax 503 in the supplied Hummel motor box. It turns a shortened 5 blade Power fin adjustable prop This installation weighs 4 1/2 pounds less than the Scott Casler VW twins, with much more "grunt". Morry Hummel's notes "Keeping it legal and light" on the original prints concern a scratch built U/C using the canopy, landing gear and engine options available at the time. The suppliers of GPS based flight instruments all have a disclaimer that these systems are to be used as backup systems only. I live in a no cell phone coverage area. Flying into one of these by chance could cause some real problems. How about mounting a classic six pack in an attache case and hanging the handle on the dash. Thank you for a great post. and for considering all the "angles"

 

[ScaleBirdsScott]

Get one of those Wing Bug or BOM Bluetooth avionics sensor packages and make it quick removable (as you can use it on any aircraft, just like a handheld radio) And use a cheap tablet as a display that plugs into a lightweight mount so that it's also removable. (Cuz it's your personal tablet computer!) Then all you have left are a few engine instruments and switches.

 

[radfordc]

The suppliers of GPS based flight instruments all have a disclaimer that these systems are to be used as backup systems only. I live in a no cell phone coverage area. Flying into one of these by chance could cause some real problems. How about mounting a classic six pack in an attache case and hanging the handle on the dash. Thank you for a great post. and for considering all the "angles"

A "classic six pack" for an UL? A Quicksilver MX normally had a clamp on tube airspeed indicator, a combo CHT/EGT gauge, a tach, and maybe an altimeter (and if you were really well equipped one of those snazzy little ball compasses that mount on the dash of your car). The lack of any of those would not "cause some real problems". Flying a UL really is a seat of the pants sort of thing that doesn't require "big airplane" tools.

 

[Bigshu]

Foam seat upholstery weight a couple of pounds, you might be able to use something lighter, an inflatable cushion instead of foam, upholstery weighs something, etc. etc.

Lots of interesting ideas. I'm not looking to make the lightest UC possible, just want to be legal. Dennis Brooks' latest UC seems to have made it handily. I will, however, have a flying suit, with padding on the backside, that is part of my personal equipment, so no pads or upholstery needed in the aircraft!

 

[Bigshu]

A "classic six pack" for an UL? A Quicksilver MX normally had a clamp on tube airspeed indicator, a combo CHT/EGT gauge, a tach, and maybe an altimeter (and if you were really well equipped one of those snazzy little ball compasses that mount on the dash of your car). The lack of any of those would not "cause some real problems". Flying a UL really is a seat of the pants sort of thing that doesn't require "big airplane" tools.

You could always use the old timey wind vane type ASI. The faster you go, the more the vane deflects. Kinda tough to calibrate!

 

[radfordc]

You claim your plane a compliant PT103 vehicle, stick to it until they burry you.

I guess it's possible that someone, somewhere has been busted by the FAA for a too heavy, too fast ultralight. I think if you come to the attention of the Feds they will find something to get you that doesn't involve them weighing or measuring speed, etc. I've never heard of it happening in the 25 or so years that I've been involved with ULs. In fact, I think the only time that ULs were attempted to be weighed was at Oshkosh, by the EAA, and it was such a fiasco that it was never repeated.

 

[Bigshu]

Get one of those Wing Bug or BOM Bluetooth avionics sensor packages and make it quick removable (as you can use it on any aircraft, just like a handheld radio) And use a cheap tablet as a display that plugs into a lightweight mount so that it's also removable. (Cuz it's your personal tablet computer!) Then all you have left are a few engine instruments and switches.

Thanks for the tip on these devices. Have you tried either of them? They both look pretty spiffy, and I like that the BOM lets you use different hardware/software rather than purely Apple based.

 

[VegasSky]

Dennis Brooks just finished another UC, and stated the dry weight at 245#. He's hoping to have a light enough canopy to install one. Lots of videos on you tube. I'm pretty sure the Hummel folks know their stuff on the weight, or else they wouldn't be able to claim its the only all metal legal ultra light. It's asking for trouble to base your whole sales approach on an easily disproved claim.

if you watch his build from start to finish, he does a few changes with lighting holes, a few rivet changes, and i think he just went with lighter wheels and tires also. from what ive seen he is able to make it with a canopy. like the plans states on the first page " think light " also Hummel did change the landing gear to steel vs aluminum not sure why but could possibly be even lighter doing Alum.

 

[Bigshu]

Hummel did change the landing gear to steel vs aluminum not sure why but could possibly be even lighter doing Alum

I was wondering about that. The gear in the videos looked different than the previous builds Dennis has done that I've seen in person. I need to pick his brain, so I can see if any of his mods would be good for my build (he's quite a bit lighter than me!).