# Power Off - 1-G vs. "Controllable" stall

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#### autopilot

##### Well-Known Member
Sorry, I thought the thread started as a discussion on the veracity and the mis/understanding of published V figures that just happened to relate to an ultralight. Am I of topic?

Unfortunately the Vcalc.com sight seems no more suspect or clear than anything else I've read, hence the confusion.
I should not have used "...level" and stuck to say 1.5 -2 degrees. Thanks BJC (0.25) and DANA for your time and input.

If it is indeed Newton we use, the answer would be 98k/hr. I now need to loose a lot of kg and increase my Wing Area. I think I need to do further research.

#### autopilot

##### Well-Known Member
Just to be sure, after I convert to Newton (mtr/sec/sec) I still have to multiply by 2?

1200 x 9.8 = 11760 x 2 = 23520 / 1.225 x 1.67 x 15
= 23520 / 30.69
=√766.37
= 26.68 m/s = 99.65 mph
At this speed I'm not quibbling about a few mph. I just can,t make it match with any published VsO for aircraft???????????
Can anyone direct me to a thread that specifically discusses wing profiles, lift and weight?

#### Dana

##### Super Moderator
Staff member
Yes, the 2 comes from the lift equation:

L = 1/2 ρ V^2 Cl S

#### 12notes

##### Well-Known Member
Log Member
Just to be sure, after I convert to Newton (mtr/sec/sec) I still have to multiply by 2?

1200 x 9.8 = 11760 x 2 = 23520 / 1.225 x 1.67 x 15
= 23520 / 30.69
=√766.37
= 26.68 m/s = 99.65 mph
At this speed I'm not quibbling about a few mph. I just can,t make it match with any published VsO for aircraft???????????
Can anyone direct me to a thread that specifically discusses wing profiles, lift and weight?
27.68 m/s = 61.9 mph (99.65 km/h).

#### Daleandee

##### Well-Known Member
Has there ever been an instance where an inspector questioned the speed of an ultralight (either stall or top speed)? I have never heard of a verified case. In fact every bit of anecdotal evidence I've seen points to the FAA not giving a fig about ULs in general.
Yep ... the old adage that the FAA cares about homicide and not so much about suicide seems to bear itself out. I'm guessing when the crash happens and the witness calls the FAA and says a tiny plane with a single seat, little motor, five gallon gas tank, and no N-number just crashed they will be told, "that's a recreational vehicle - call your local sheriff."

The story years ago from Sun-N-Fun was the FAA guy looking over a Titan Tornado that was single seat with a Rotax 503 on it. On the panel was a sign that read, "empty weight 253.6 lbs - gross weight 550 lbs." The FAA guy looked it over and said, "nice ultralight" and went about his business.

But I also believe that just because they turn a blind eye or let some of this slide is not a reason to flaunt any open defiance of the rule.

Dale

#### Turd Ferguson

##### Well-Known Member
The story years ago from Sun-N-Fun was the FAA guy looking over a Titan Tornado that was single seat with a Rotax 503 on it. On the panel was a sign that read, "empty weight 253.6 lbs - gross weight 550 lbs." The FAA guy looked it over and said, "nice ultralight" and went about his business.

But I also believe that just because they turn a blind eye or let some of this slide is not a reason to flaunt any open defiance of the rule.
Not so much turning a blind eye as much as following directions. FAA inspectors are directed not to pursue enforcement actions at an aviation event unless someone is in imminent danger.
The FSDO where I live typically does not do surveillance on ultralight operations unless there is a complaint or accident. That is directly from the FSDO manager.

Good story nonetheless.

#### TFF

##### Well-Known Member
We had a crash of a LSA plane right when LSA rules came into effect. News helicopters and all. When the FAA got there, the pilot told them it was a an ultralight. They got in their car and left. The pile looked UL enough that they just walked away. Note, the pilot was on his 10-11 crash so they did not see anything they hadn’t seen.

#### Daleandee

##### Well-Known Member
Not so much turning a blind eye as much as following directions. FAA inspectors are directed not to pursue enforcement actions at an aviation event unless someone is in imminent danger.
The FSDO where I live typically does not do surveillance on ultralight operations unless there is a complaint or accident. That is directly from the FSDO manager.

Good story nonetheless.
I've heard it said before that the FAA takes a hands off approach at events unless there is a glaring need to do so. The times I've had to deal with FSDO I found them to be easy enough to work with and rather pleasant folks. Of course if I was talking to them because I forced landed in a school yard after running out of fuel I'm certain the conversation would be very different!

#### BJC

##### Well-Known Member
HBA Supporter
The FAA is no different from most large bureaucracies; full of good people constrained by rules, regulations and SOP, plus a few jerks. It is the jerk that you hope never to need to deal with.

BJC

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#### pictsidhe

##### Well-Known Member
i have heard numerous tales of the FAA conducting undocumented enforcement. Derswede told me one of them after his friend did something unwise in the pattern.
What seems to happen is that when an FAA guy comes across an illegal ultralight, he tells the pilot that they can do one of three things. Either meet the regs, stop flying it, or face the horrific fine if they decide to keep flaunting and get it crushed. These incidents are not on public record. Nobody seems to be stupid enough to keep flying after being told what will happen if they do without being legal. So, no publicly documented enforcement.

#### bmcj

##### Well-Known Member
HBA Supporter
Of course if I was talking to them because I forced landed in a school yard after running out of fuel I'm certain the conversation would be very different!
We had a two-seater (kind of like an ultralight, but heavier and N-numbered). We put it down in a small elementary school playground after a drivetrain failure (it was a Saturday). It didn’t even get the attention of the adjoining neighbors. We had someone bring parts and tools, and did a field repair before flying it out of the schoolyard (flew out solo due to the short field). On Monday, we notified the guys at the local FAA GADO office (we had a good working relationship with them and they considered this as a training ultralight). Their answer was as long as no one was hurt and there was no property damage, there was no need to file a report.

#### 12notes

##### Well-Known Member
Log Member
I think it's a good policy to file a NASA report every single time something that could possibly be interpreted as a potential violation. It's kind of like buying a "get out of jail free" card after possibly speeding past a speed camera. I filed one after landing a glider in a soybean field, no damage to the glider, not even close to an FAA incident, but the farmer insisted on calling the police, and somehow the local paper printed that the "crash" damaged a Ford F-150.

##### Well-Known Member
What seems to happen is that when an FAA guy comes across an illegal ultralight, he tells the pilot that they can do one of three things. Either meet the regs, stop flying it, or face the horrific fine if they decide to keep flaunting and get it crushed. These incidents are not on public record. Nobody seems to be stupid enough to keep flying after being told what will happen if they do without being legal. So, no publicly documented enforcement.
Some years back a fellow named Max Rentz built a plane called a Tiger Cub. Nice plane but not what most people would think of when the term "ultralight" is used. More like a little Piper Cub. Max was operating his plane under Part 103 until a couple of FAA guys happened to visit one day and questioned him about why no N number. They suggested he not fly it again until he got right with the law.

##### Well-Known Member
We had a two-seater (kind of like an ultralight, but heavier and N-numbered). We put it down in a small elementary school playground after a drivetrain failure (it was a Saturday). It didn’t even get the attention of the adjoining neighbors.
Our guy wasn't that lucky. He is a licensed pilot but was flying an unlicensed two place UL-ish plane. One Easter he agreed to do a candy eqq drop for some kids. He made his approach to the field but as he tried to drop the candy he inadvertently hit the engine kill switch and ended up in the top of a tree. No harm to him, but the authorities and news media came to see the show. FAA admonished him, suspended his certificate for a few months, and required him to get some remedial training. No fines.

#### Dana

##### Super Moderator
Staff member
Usually the FAA gives you a choice between a suspension and fines.

#1 rule if you're flying an obvious fat ultralight, don't do anything to attract attention.

#### Lendo

##### Well-Known Member
Autopilot - Theory of Wing Design by Abbott and Von Donenhoff, It's considerdd the Bible of Airfoils. Also Riblett Airfoils.
Converting from Cl (2D Airfoil) to CL (3D wing) multiply by 0.73 i.e. [0.93*(Pi/4)]
When Calculating for S (wing area) use the 3D figure following the format presented by Dana i.e. S = Aircraft Weight(W)/ (0.5*P (density)*CL (3D) *V^2).
Your Lift (CL) should be conservative as opposed to optimistic and you should use the additional Cl (for Flaps) if calculating for Stall Speed Wing Area in the case of using Flaps - as we do in Australia.
Simple yes!
George

#### Lendo

##### Well-Known Member
as we do in Australia - for Landing Speed, as in the case of 45 Knots for Light Aircraft
George

#### User27

##### Active Member
Occasionally some real gems get posted here, I've never come across Abbott and Von Doenhoff before, but its available from several sources as a download. Excellent. I've also never seen a straight forward method for taking into account 3D flow when estimating stall speeds (or required wing area).
Many thanks on both counts!!

#### Turd Ferguson

##### Well-Known Member
I think it's a good policy to file a NASA report every single time something that could possibly be interpreted as a potential violation. It's kind of like buying a "get out of jail free" card after possibly speeding past a speed camera. I filed one after landing a glider in a soybean field, no damage to the glider, not even close to an FAA incident, but the farmer insisted on calling the police, and somehow the local paper printed that the "crash" damaged a Ford F-150.
A NASA ASRS form is helpful for an inadvertent violation of the FARs. If one chooses to fly an overweight or otherwise 'illegal' ultralight (the FAA will call it an unregistered aircraft) it will be difficult at best to show that was an inadvertent transgression of the regs.

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