pilotdave

Never done a balloon jump, but I definitely broke my record for farthest off landing yesterday. Did a cross country. Left the plane at 12,000 feet, 12 nautical miles (~15 mi) from the DZ. Couldn't even see the DZ till I was about half way back. At around 3000 feet I was still a couple miles out, with some woods between me and the DZ. Had a nice back yard underneath me, so I just held into the wind. Backed up a little, but mostly just came straight down. The yard I was landing in was surrounded by very tall trees. I was as far downwind from the treeline as I could get, but got some really nasty turbulence around 300 feet. Canopy suddenly turned almost 180 degrees on me. Recovered from that, turned around, and made a soft landing. The family came out and offered me a ride back to the DZ. I didn't bother calling the DZ since I thought I'd be back in just a couple minutes. Didn't realize it was gonna be like a 7 minute drive. As we pulled onto the airport, we saw a state police helicopter. The woman driving asked if that was for me. I said no, they'd never waste their time on me. Turns out I was wrong. They were doing a training flight and our jump pilot asked if they wanted to help search for me. They were called off when I came strolling back onto the DZ. Definitely a fun jump, but scary as hell! Dave

I'd be pretty pissed if no riggers would tighten my poptop just cause it was packed by someone else. It's just not always possible to have the rigger tighten it, and getting a repack cause my poptop was loose is ridiculous. I'd tighten it myself if a rigger wouldnt do it, but it would be safer for a competent rigger to do it. Dave

Your instructor will have the best advice for what canopy you should be flying, but if he's the one selling, it's hard to know who to trust. It's like getting a diamond appraised by the jeweler that wants to buy it from you. If multiple instructors that know you and have seen you jump say its a good canopy for you, then it's up to you to decide if you're comfortable. But if the instructors say "it's probably maybe alright for you, just dont do anything stupid," look elsewhere. But just be wary of the seller telling you what's right for you... I ended up with a 120 reserve in my first rig (not THAT small for me...but smaller than comfortable) when the dealer/my ex rigger happened to have a container for sale that holds a 120 reserve. Now I didn't hear any objections to that from my instructors so maybe it wasn't a horrible choice, but when I bought my second rig, I upsized a bit. Dave

You can save a little money with an FT-50 but you can't go wrong with an altimaster. The FT-50 has a little bigger face than the older altimasters, but I think the new ones are about as big. And you can get a free custom face plate on an alti-3 if you want something that looks a little different. Dave

Awww geez... c'mon physics boy... We've got 4 forces, right? Thrust, drag, lift, and weight. What happens when thrust is greater than drag? We accelerate. What happens as drag increases to finally match thrust? We stop accelerating. Meaning we maintain a constant speed. Well what happens when lift is greater than weight? We accelerate upward. Well now it gets comlicated since we've got an upward component of thrust and a downward component of drag. But for simplicity lets just assume the climb is shallow so the upward thrust and the downward component of drag are minimal. As long as L>W, the aircraft will accelerate upward. But what's gonna happen? Eventually an equilibrium will be reached, right? Can't accelerate upward forever (unless you're flying a space shuttle). Once you've entered a steady climb rate, your upward lift is equal to your weight. Your total lift could be higher, but the lift that actually pulls you upward is not. Dave

Net lift may be defined as perpendicular to direction of travel, but I was talking about the vertical component of lift. Again, disregarding the vertical component of drag, which I think is reasonable for shallow descent angles and speeds, the vertical component of lift equals weight for any wing in unnaccelerated flight. Even a wing in a constant rate climb or descent has to be producing a vertical component of lift equal to the weight. Otherwise vertical forces would be out of balance and the wing would be accelerating. Dave

Hehe... I was kidding... but since you asked... Wind tunnel models can give descent results, but if you need exact results, the model needs to have the same geometry (obviously), and the mach number and reynolds number need to be the same as the flow you are simulating. This can be done using pressurized or chilled wind tunnels. Dave

my DZ has a super otter and 182. I don't do many 182 jumps, but I get my fill over the winter and on slow days. Did a bunch of em last weekend though. For a hop n' pop, a 182 is great. Climb out on the strut, let go, and you're perfectly stable instantly. Did a couple 4 ways out of it too. I was way out at the end of the step. Tried to shimmy my left foot a little closer to the edge of the step, and slipped. So then I had to wait for the 3 others to climb out there while I hung from the strut. Actually worked great though. 182 jumps always seem more "personal." The pilot is right there next to you, so its much easier to know what's going on...as opposed to waiting for a green light. I enjoy occasional cessna jumps, but I'm sure glad they are few and far between! Dave

You don't want me to start with scaling effect/reynolds numbers... Dave

No clue what parachute manufacturers use (if this type of analysis is even done). But my guess would be they do something similar to how flaps on planes are analyzed. Coefficient of lift is a made up measure of how much lift a wing can produce. When flaps are dropped, Coefficient of lift isn't really "recalculated" based on the new wing shape. It is compared to the coefficient of lift of the original wing shape. In other words... fowler flaps increase wing area, which is part of the calculation of C_L. But when determining the effect of flaps, wing area is held constant. If you used two different wing areas, their C_L's wouldn't be directly comparable. So my guess for parachutes is that angle of attack is held constant as the brakes are pulled, and the theoretical lift, based on that "arbitrary" angle of attack, can be measured. Could be wrong though! Edit before someone bashes me... Yes I know wing area is needed to calculate LIFT, not coefficient of lift. But usually we'd be back tracking using wind tunnel test results which start with lift, and you need to figure out coefficient of lift. And Quade... an airfoil CAN produce zero lift at a negative angle of attack. I'm NOT talking about angle of incidence. A symmetrical airfoil produces no lift when AOA=0. But any airfoil with positive camber produces SOME lift at AOA=0. Therefore in order to produce zero lift, AOA has to be negative. Seems strange, but it's true. Dave

It works but that's not what is normally used. Most airplanes are said to generate zero lift at a negative angle of attack. SOME reference line must be used. Normally the chord line is chosen. For a non-symmetric airfoil, the zero lift angle of attack will be negative. It's easy to find lift slope curves (lift vs angle of attack) for most standard airfoils, and I think they all base AOA on the chord line. That way the lift at zero angle of attack is visible on the graph. If AOA was defined based on the zero lift angle of attack, it would be impossible to compare two airfoils on the same graph. Dave

I'd answer that but references to pedophelia aren't allowed... Dave

WRONG! Square1 sucks! Everyone should buy from arlo!

Not sure if this link is gonna work...https://www.nasdac.faa.gov/pls/nasdac/NASDAC.wwa_app_module.show?p_sessionid=126769 This is a search tool for the Aviation Safety Reporting System (ASRS). These are reports mostly filed by pilots after they either did something unsafe (and probably illegal) or witnessed something unsafe. Pilots file these reports because they act like a "get out of jail free card" in some cases. Basically when a pilot does something dumb and thinks the FAA might suspend his license, he can quickly file an ASRS report and confess. In exchange for the invaluable information, the FAA, in some cases, lets the pilot off the hook. Well do a search for "skydiving" (narrative search field). Take a look at what your neighbor pilots are saying about you and your DZ. Think nobody noticed when you jumped through a cloud? Think again. Dave

Who cares? You're not landing with the plane!

Yeah, way up above I mentioned I wasn't taking drag into account so saying the two canopies have equal lift isn't exactly true. But for small descent angles and low speeds (like parachutes), I don't think the vertical component of drag will make a huge difference in the amount of lift that each canopy needs to generate. And teason... Forget that drag stuff for a min. When I say the lifts are gonna be equal, I'm only talking vertical component of lift, not total lift. If the braked canopy created more lift vertically than the exit weight of the jumper, the canopy would accelerate upward. Course that's exactly what it does right when you pull the brakes. But when you leave them down, the canopy will eventually reach a steady state. At that point, the lift equals the exit weight. If the vertical component of lift doesn't exactly equal weight, the canopy will accelerate up or down. For a plane in a steep dive, drag becomes very important. But a plane at a very shallow descent angle, which is not accelerating vertically, is producing the same amount of vertical lift as a plane flying straight and level. Dave

I had grocery store sushi tonight. Little bit scary, but it was actually pretty good. Dave

Nope, just added the booties to my existing jumpsuit. Doesn't make much sense to me (legs in more is my only guess). But the booties definitely sped me up. On my first jump with the booties, I was doing a 5 way I think, and wearing my weight vest. Approached my slot, and just as I was about to dock, I sunk right out. Going low isn't something I was used to. I was pretty baffled by it. Same exact thing happened again later on. I've always been much more likely to float if I reach for a grip or something. So I started thinking about what was happening. Best I could come up with is that I was approaching the formation with my legs out a bit. When I got close to the formation, I pulled my legs in a little to stop the forward motion. Legs up, less drag, dropped out. So I dropped the weights and haven't needed em since except for a 2 way with a really fast faller. Every time I've been suckered into wearing weights on an RW jump since getting the booties, I've gone low. Haven't had any trouble getting down to a formation since then either. So I might be wrong about why the booties are speeding me up, but that's what happened. Dave

BTW... I like that feature. I don't feel so bad posting long ass URLs anymore.

Cl/Cd = Lift/Drag ratio. Glide ratio is basically the same thing as lift to drag ratio. If pulling half brakes changes lift by the same factor it changes drag, your L/D ratio won't change. In reality I doubt that would ever happen, but it's possible. And maybe I'm just missing something here, but how do you know a canopy at half brakes flies at a lower angle of attack than a canopy in full flight? I'd assume otherwise, but maybe I'd assume wrong. What am I missing? Dave

Not sure if this fully answers your question, but here's what the NTSB says about reporting accidents (NTSB 830): And the definition of an aircraft accident is: Substantial damage is defined as: Dave

And how long is that gonna take? Yes, initially the braked canopy will create more lift, but once it has reached an equilibrium, it will create the same amount of lift as the unbraked canopy...by flying at a lower airspeed, etc. What happens for the few seconds after the brakes are applied has little bearing on the question at hand. Course neither does the fact that both canopies generate the same amount of lift. But, the braked canopy doesn't have a lower descent rate because it generates more lift. That's the point I'm trying to make. Dave

Both canopies are producing the same amount of lift... L=weight for any wing in unnaccelerated flight. If L

Pulling the brakes changes the effective camber of the airfoil, not really the thickness ratio. It's like putting the flaps down on a plane. Completely changes the L/D ratio and should change the glide ratio. Experience might tell you that it's not a very big change in glide ratio.... I don't know. Dave

If A will lose altitude faster, why will B land first? Dave