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Blue on Top

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Everything posted by Blue on Top

  1. Just to let people know and trying to get back on topic, scheduled service (airlines) and GA calculate performance differently. An airline calculates performance based on the runway length that they are flying in and out of. GA airplanes calculate the shortest possible runway length. To further breakdown the GA portion, business jets (part 23 and 25) publish in the AFM, the LONGEST of three distances: 1) accelerate-go (engine fails (or master warning) at Vef (several knots below V1) and pilot has decided by V1 to continue to go airborne, 2) accelerate-stop (engine fails at Vef and pilot has already taken action to stop before reaching V1) or 1.15 times the accelerate-go with all engines operating normally. (back on topic) For us single engine folks, today we publish the data that was acquired from the prototype airplane. No new engine. No higher power engine. Just the engine on the day the testing was performed. You should be able to beat the AFM/POH numbers. The big boys MUST meet the AFM numbers (AFMs are conservative). Another big factor is that the OEM must cross the end of the runway at 50' on the 3 degree glide slope … which adds ~1000 feet of runway (this is also why you see all the tire rubber at the 1000 foot marker at major airports. You don't need to be at 50' over the threshold. Failures (and improperly configured airplanes) are not accounted for in our single engine airplanes.
  2. @Ibra If I typed 1.33*Vso, it was an accident/typo. It should be 1.3*Vso … or 1.3*Vs1 for approach. On high-powered, newer, twin, turbofan engine airplanes, the AFM may have Vapp or Vref greater than 1.3*Vs because Vmcl (minimum control speed in the landing configuration) might bump the speeds up. This is also why the pilot is required to use the published/approved numbers and not simply 1.3*Vs. And, before I get flamed again, yes, some systems on very expensive airliners automatically calculate/know this inccrease.
  3. @Andy95W Thank you for your level-headed explanations. 1. I agree with your statement. But, if this were known and trained, why did the crew continue to keep the airplane in the stall? AOA told them the aircraft was stalling/stalled (until airspeed went below the low airspeed threshold and invalidated AOA, too, but it too came back on the way down … when the pitot tube heaters caught up with the ice pellets and cleared again). 2. Yes, again. As a very educated guess, I would highly doubt that simultaneous failure of 3 pitot tubes was ever analyzed before this event. It would also have to be a failure (icing) that completely blocked the pitot tubes, but at sometime the drain holes were open(ed) to bleed off the indicated airspeed. 3. So I can learn, are you saying that either "normal law" allowed the airplane to stall or that the airplane left "normal law" and allowed the airplane to stall? Thanks! -Ron PS. Pitot heat on or off is not relevant to the cause of this accident. All 3 pitot tubes were overwhelmed with ice. Pitot tube certification regulations (I know in the US) have been changed to handle this new requirement.
  4. @GeeBee It's a great video. I've watched it several times before … and now once again. Love it. It's also a great reminder that we don't need more stall or spin recovery training … it won't help. (side note: everyone should do at least one spin. It won't help you in the pattern, but maybe it wont scare you as much if it actually happens … at a high enough altitude). We need training to know what to do BEFORE the throttle is moved forward for takeoff. And train that. And train that. And train that. And train go-arounds. And train go-arounds, And train go-arounds. And train about departure stalls … with and without an engine failure. And train that on climb out if one banks the airplane they must be able to accept some loss of rate of climb. Etc. I don't agree with the 1.404 Vs, and pilots should not be taught this. Airlines (and GA) should be teaching 1.3Vs, that is what their landing performance is based on. Too many people add knots for crosswinds, knots for gust (good idea), knots for "safety" (which is not true), knots for grandma, knots for etc. This is a major reason for airplanes going off the end or side of the runway. And for Mooney airplanes floating into the next county. I would name an OEM that it happens to more often than others, but it's not the OEM's fault. On the 1.404 Vs, in particular, it is adding knots where knots are not required. 30 degree bank does not equal 8% stall speed increase; 60 degree bank does not equal 40% stall speed increase. Those numbers are only for level flight and pulling those related G-loads … 2G in the 60 degree bank case. People might be banking 60 degrees in the base-to-final turn but are not pulling 2G. In fact they are probably pulling slightly over one G. The problem there is the rate of descent is very high … and pulling only tightens the spiral. BTW, the base-to-final turn produces about 5% of the fatal accidents. The Industry is finally looking at the real numbers and starting to realize this fact. Takeoff, go-around and moose turns (low altitude, ground-reference maneuvers … looking at your house, girl friend, showing off, etc.)
  5. @tmo First and foremost, thank you. Secondly, I think you're following along very well. So … on that high wing Mooney (you've just started a good rumor ) ... We will start thinking in 2D (2 dimensions) with a "typical" wing (an airfoil), the type all pilots are taught about. As angle of attack is increased, airflow starts to separate at the trailing edge. The point of separation moves forward as AOA increases further At stall AOA, lift drops off some, and drag goes up significantly. Now comes the part we need to think a little more about. It's not hard, but we'll add the fuselage into the equation. Looking from the top, the fuselage is shaped similarly to a symmetrical airfoil (it's not truly symmetrical, but we will say it is). Now we simply put the fuselage down on top of the wing. If the fuselage is getting smaller (suction) while over the top of the wing (suction side), airflow will want to separate earlier … causing more drag. Both the wing (locally) and the side of the fuselage (locally) will separate, causing lots more drag. A high wing doesn't have that issue because the fuselage is on the pressure side of the wing. Now, before y'all run off and say, "Ron said Mooney airplanes should have high wings." … if life were that easy … EVERYTHING in design is a tradeoff/compromise. Where is the landing gear going to go now? How do I get mechanical flaps to operate? Etc.
  6. @GeeBee Google it. Up against (AOA) no-stall limit. I'm guessing you have a different reason. Is that a "normal" operation? No, not in my opinion; it was showing off aircraft performance. Is it a possible emergency go-around maneuver? Yes.
  7. @PT20J Thanks! I'll read the NASA report … tomorrow (when I am more coherent). @cliffy 1. He used the NLF airfoil of his choice. The under-cambered ailerons are a fallout. 2. Yes, that's why I said 10 UP and 5 down. Mooney ailerons are VERY differential to reduce adverse yaw. TCDS travels show this clearly. 3. Agree with you, but I don't know how much. That seems high to me, but you would know more. Does an UP aileron put the long, wing, aileron push-pull tube in compression? That would explain the high amount of float. 4. Small bulbs are for strength (aka Cessna). Vertical dimension (and shape) will determine centering/control "stiffness" 5. Ummmmm … don't want to burst your bubble, but the composite shell is more expensive, more labor intensive and heavier. As far as drag goes, well … it isn't less. Sorry. We can talk in person about why all is as it is. 6. You might be surprised on which little things cause drag (and which big ones don't ). Low wings are inherently more draggy because of the wing fuselage interference drag and reducing fuselage width before the trailing edge of the wing .. without a really big fairing. I really love all y'all's comments. I learn so much from all of you. Thanks! Ron
  8. @GeeBee 1, 2, 3 The WRONG thing. They need to be trained better. Push … like ALL 100 glider pilots will do. The time to think about it isn't when it just happened. It's in training and again before the power is pushed up.
  9. 1. In 3 words, more available performance. As I mentioned previously, each airplane is different and each design has different reasons for different systems. For an airliner that only flies out of few, paved, runways that are much longer than is required, sure, don't let them stall …. but then the pilots won't … better not go there. You may remember an accident at the Paris Airshow with an A320 that those pilots might disagree with you. Again, full automation is coming. Pilots rely on systems to fly the airplane way to much the way it is now. 2. I ordered the book. I've read the actual transcripts and reviewed the actual cockpit data. I'm looking forward to reading your friend's book. 3. The training should not be on how to turn the autopilot on and use the FMS. It should be on what happens when the automation fails and why the automation failed. Had AF447 crew known that AOA and airspeed are totally independent, would they have still ignored the stick shakers? They knew some things as they turned the pitot heaters on during the descent. Bottom line: I'm looking forward to reading the book. AND finding a solution(s) that doesn't allow accidents like this.
  10. @PT20J @carusoam @M20Doc I would have guessed that, but ... The lateral-directional regulation is .. ridiculous. "Unreasonable" is probably a better word. We (ASTM) is looking at a way to redefine the required testing … which will eliminate the need for rudder-aileron interconnects. This is why I started that thread earlier. Lateral-Directional stability by the way we test it is not necessarily good. In fact a slightly unstable airplane is more controllable, which is what we want. The original regulation was written to make sure the airplane could be flown home with any flight control disconnected. In this case the rudder or aileron can be disconnected and the airplane can be flown to a runway. Sweep and/or dihedral takes care of this normally. BTW (and as a funny note), the new regulation states, "The airplane must have stability." LOL . What the hey? Negative is "stability", too! Also pitch phugoid mode doesn't need to be damped (positive) either. Go figure!
  11. @PT20J and @cliffy This is interesting. I should think about this more, but off the top of my head the trailing edges should be as small/sharp as possible for minimum drag (at these speeds). Thicker trailing edges make the surface more stable … at the cost of drag … similar to adding a T-strip. Both will have a tendency to center the surface when the controls are let go (stick free). The more centering, the more force would be required to move the surface. Changing the TE to more pointed will cause the lateral-directional stability to not be as good. IOW, the aileron will not return to neutral when let go. Aft camber (of the wing but showing up as a cusp on the aileron) will aft load the airfoil. An NLF airfoil is typically/already aft loaded. This will not increase/decrease the aileron forces as the opposing aileron is helping it, and the ailerons act as a loop (yes, the system is push-pull tubes, but …). Aft loading will cause the ailerons to "float" more, but in a Mooney that just means that all the aileron control system free-play is taken out in that direction. So … when roll control is input is made, the down-going aileron will move first. This is totally irrelevant as we typically only care about what is called "total aileron". IOW (for roll control), a degree of UP travel equals a degree of DOWN travel; we add the two for calculations. IOW, if the left aileron goes up 10 degrees and the right goes down 5 degrees, we use 15 degrees of aileron travel. Hope this helps, but I'm guessing I have added confusion. Blue on Top, Ron
  12. @PT20J Skip: You are not mistaken! You are correct. But, no one said that all tails are created equally or have exactly the same stability, which also includes factors for wing area, wing chord and dihedral. Many, many factors play with many, many other factors … especially when dealing with lateral AND directional issues that are coupled. It's not simple, cut and dried. For example, yaw/roll coupling is very wing sweep dependent, whether it be rearward or forward sweep. We typically think of sweep as stabilizing (yaw and roll in the same direction), but forward sweep (X-29, Moonies, Blanik sailplane, etc.) is destabilizing (yaw and roll in opposite directions).
  13. @0TreeLemur and all. These aerodynamics are actually a complicated subject (especially when talking about spin aerodynamics … it is not as easy as the books (so far) have stated, but we are getting closer with CFD … what one can trust of them. On the simplest portion, the vertical flying with attached airflow, the most effective surface will be the one with the 25% chord most perpendicular to the airflow. Spin characteristics and airflow are a completely different animal and depends on many, many other factors, such as: the horizontal surface - shape and location, the aft fuselage - shape, location, edges, etc., horizontal/rudder interface, fuselage/rudder interface, etc., etc, (meaning there's a lot more! We have proven that the NASA formula for spin recovery is incorrect … or at least not complete. This is why we are still required to spin the airplanes in all configurations. We just don't know enough yet.
  14. I'd be happy to join the fight. And, yes, even modestly, I know my sh** (aerodynamics). Will you post the offending material? Or a link to it? Thanks! I know I don't count, but I have given talks across the nation on the Mooney tail and why it is designed as such. Send the wiki editor to Oshkosh or SNF, I'll teach him/her a thing or two! LOL LOL Isn't it amazing how tough I sound on the internet
  15. If anyone has Peter Garrison's contact information, I would appreciate it. He has a lot of great information, and I want him to personalize one of his books that I own. Great guy. I WILL find the ad. It's somewhere in a box in the basement … made more confusing by the moves from Chino, CA to Kerrville, TX for 6 weeks and now in Wichita.
  16. 1. Yes, we should warn the pilot before the aircraft stalls. No, I do not want to prevent the airplane from stalling … unless it has really, really bad stall characteristics. Each airplane is different, and there pros/cons/exceptions on every rule and train of thought. 2. And this is exactly what AF447 flight crew did. The problem was they didn't train well enough to know that the airplane was not in "normal" mode. They applied flight controls for the airplane being in "normal" mode (full power, full aft stick for stall recovery), which the airplane was not in "normal" mode. On a sad note, the airplane gave them exactly what they asked for … full up elevator. Several good books, at least one TV show (with the NTSB) and the transcripts/flight and voice recorder data are publicly available. 3. On the Max, Boeing made several big mistakes. Too complicated to get into here, Bottom line for me is that those accidents had multiple links in the accident chain. If any link would have been broken, the accidents would not have happened. Everyone is now pointing at everyone else saying, "If you would have performed perfectly, you could have prevented this." That goes for everyone involved: Boeing, FAA, flight crews, maintenance crews, etc. On a serious note, the more we automate airplanes, the less involved and trained pilots will become. The "autonomous/autopilots" can no longer give the airplane back to the pilot when something fails because the pilot is the weakest link in those airplanes. I want to involve the pilot more.
  17. @0TreeLemur Fred: I feel for you. I have heard of that Al Mooney referenced article, too, but I have never seen it. Somewhere I have a Mooney advertisement that has a lady sitting on the tail (it's a black and white drawing), and it explains the tail, too. If it helps at all, I have a degree in Aeronautical/Astronautical Engineering from a major university, and I have formed, managed and supervised Aerodynamics and Flight Test department from coast to coast and border to border, literally I was also a Chief Engineer for Mooney (on the M10), if that helps your case , Sorry, yes I know that it won't. Keep up the good fight. he truth will win!
  18. @GeeBee I guess we have a different understanding of the story and how the system works. In my understanding, MCAS is not part of any trim system (nor are trim systems allowed to run the stabilizer this rapidly). Fighting the MCAS system will aggravate it and cause it to run the stabilizer at twice the original rate, which the original rate is similar to a stick pusher (except MCAS is not over-ridable). Although MCAS uses the stabilizer actuator, it accomplishes the task through a completely different system (MCAS, not trim). (quoted from your article) "Schulze said Boeing assumed in its testing that pilots would “immediately identify (the MCAS) unintended trim action” and then “immediately take action” to counter it, by using thumb switches on the control column to pull the nose back up and if necessary to hit two cutoff switches and stop all automatic stabilizer movement." How should the pilots have identified a system that they didn't know about, nor is it in the Flight Manual? Again, it is not trim. Again, the column switches will do nothing to stop MCAS. (more from the article) Boeing’s assumptions proved wrong. With those distractions in the cockpit— and in the case of the Lion Air flight, with the crew having no prior knowledge of MCAS, which Boeing had omitted from the flight manuals — the pilots did not diagnose the problem they were facing and failed to respond as Boeing expected. Ironically, the MCAS issue and AF447 (I noticed from your comments that you're an Airbus fan), have nothing to do with configuration warnings. The AF447 accident was a simple, don't pull the stick back to the aft stop when the airplane is stalled. We all learned that in our first couple hours of private pilot training. That very experience crew didn't know that the airspeed system and the stall warning systems are completely independent of each other. Looking at the NTSB data for fatal accidents, one will find that the vast majority are during takeoff and go-around (not landing) and maneuvering (showing off at low altitude and moose turns). We need a solution; what are your ideas? PS. If you would like to start a thread about MCAS (I believe there already is one) or the AF447 accident, I would be glad to participate in those, too. PS2. There have been 2 accidents in my state in the past 6 months that I know about that killed two people - one in an M20 and another in a Bonanza. The Bonanza was trimmed nearly full nose up on takeoff.
  19. @Yetti Yep. Total integration is not always a good thing. The Hawker Beechcraft Corporation "Hawker Horizon/4000" and the Cessna Citation Sovereign both have the Honeywell EPIC system in them. One is fully integrated; the other is not. One airplane is still in production; the other is not. Same stuff on my Honda "Pilot" (but I love her still).
  20. @cliffy Yes, your intuition is correct, but an end plate would have very little effect. The flow would just "plan ahead" and go there more directly/straightly, leaving a vortex at the inside corner of the end plate. Remember the fuselage and horizontal surfaces are pretty big. Similar to winglets, end plates have to be fairly large (and laying them flat -extending the wing- is much more efficient). On a wing , the higher and lower pressure sides are known … yes, unless flying inverted . Thanks!
  21. @0TreeLemur Fred: There is probably not an easy to understand book to read that will talk about span-wise flow, but I'll give it a quick shot. Before we start, flow direction does not determine pressures but is a result and indicator of pressures. Let's talk with respect to just the forward swept Mooney tail and rudder. (talking about the whole vertical surface) Aerodynamicists only care about the 25% chord line. The Mooney vertical surface is swept slightly forward, even at higher angles of attack and made more forward swept locally by the wing downwash … especially with flaps. The surface is more effective the closer the local airflow gets to perpendicular to the 25% chord line. Simple, right? Now lets look at the rudder and its hinge line. Let's start with a hinge line that is perpendicular (90 degrees) to the airflow. As the rudder is deflected (we'll say to the right), a higher pressure will form on the right side of the vertical surface. Because the whole surface is (typically) tapered, a higher pressure will form at the base than at the tip, and flow will start to turn upward (an indication of where the relatively lower pressure is). Even if the surface is not tapered this will still be the case because nothing is in the way of the airflow going off the tip (just like a wing tip vortex). The further the rudder is deflected, the more this flow will turn upward. Note: I haven't mentioned pressure changes … yet. Now, let's sweep the tail/rudder hinge line aft (jet, go-fast look). We've now made it easier for the flow to travel up the rudder hinge line and off the tip. Again, we're not losing pressure. (note: it is less effective because the 25% chord line is swept). Now, let's sweep the tail/rudder hinge line forward (Mooney, Lark, etc.). We've now made it harder for flow to travel up the rudder hinge line and off the tip. In fact, we're forcing the flow to travel down the hinge line (something it doesn't want to do). In this case, the pressure does increase because we are forcing the flow to do something it doesn't want to do … travel INTO higher pressure. In addition, the base of the vertical has a endplate called the fuselage and horizontal stabilizer, which makes it harder yet! I hope this helps. BONUS, BONUS, BONUS (just in): If you're going to Sun-N-Fun, I'll be giving a forum, "Demythifying Stall and AOA" on Wednesday and Saturday at 9AM. I think they missed my "De-Tail - Mooney (and all other GA) Aerodynamics" application. I'm "talking" with them now about doing the Mooney one on Thursday and Saturday at 1PM both days. Either way, I'll be at SNF all week.
  22. @bradp Great observation! Yes, but it kind of depends on what all the system does. Here's a simple way to look at it. If the original device was required to certify the airplane, no; it cannot be installed under NORSEE (Non-required Safety Enhancing Equipment). If it is additional information, yes it can be installed under NORSEE. I'll try to give an example. A device that looks at flap position and throttle position as a "takeoff" or "go-around" warning system can be NORSEE installed. IF that same system is used to show flap position (replaces the mechanical cable in the case of a Mooney) it must have an STC and cannot be installed as NORSEE. IOW, the flap indicator is required by regulation. Another really good example (and I am saying this to help people understand NORSEE … and not get off topic) is the new electronic attitude indicators. The new attitude indicator function itself is not NORSEE (an attitude indicator is a required instrument). All the information around it (airspeed, altitude, slip indicator , etc.) is NORSEE. Here's the kicker. NORSEE information is not required to be correct … nor to even function or be there. IOW (and different units/companies do this differently) for example, airspeed on a new all-in-one unit is not required to be correct (you are required by law to still have a TSOd airspeed indicator) … unless the company that made your all-in-one has TSOd and certificated the airspeed function of that unit. This is true of all the surrounding data. Confusing I know, but once people understand it is very straight-forward. Did this help?
  23. @GeeBee The Boeing MCAS debacle is much, much more complicated than what is known on the surface by the general public (me included ... but I know certification and of these systems in particular very well), but the MCAS system is also a great example of NO WARNING. The system just takes over control without any warning. To support your viewpoint and in the MCAS case specifically, these 2 fatal accidents should have easily been avoided and not been a problem at all. The crew could have handled the situation easily by simply turning off power to the stabilizer trim motor (not the autopilot, not the trim system, the electric motor that drives the stabilizer). The flight crews on a few flights before the accident did exactly that on this exact same airplane. PS. I am a big fan of "dark cockpit" design philosophy. Don't tell the pilot anything that he/she can't do anything about. PS2. I am also a big fan of simplicity, lightness and robust systems that tell the pilot/mechanic what is wrong (or causing the issue).
  24. @chriscalandro LOL. So true. As we say (less politically correctly) in the industry, if we design an idiot-proof system, a better idiot will come along.
  25. @Skates97 Thank you! This is a fantastic data point and wonderful observations! I believe that practicing (as you have done) is a great way to be more aware of what could happen and how to deal with it. Practicing go-arounds are an eye-opener too.
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