jlunseth

Totally true. Straight ahead stalls are benign and take some time to develop. Cross controlled and accelerated stalls are immediate, violent and you are upside down in the first turn of a spin faster than I can write that.

I have built in O2. I bought four of the Precise Flight oxymizer systems and awhile later one of the Aerox mic'd masks. I have quite alot of hours on both, although the more Angel Flight flying I do the less I go up into the oxygen altitudes because the flights are not that long and I don't want to risk patients who may already be compromised. The best part about the Precise Flight system, or any other free-flow system for that matter, is the ball-type flow meter. You have it in your lap and if you start wondering if your O2 is working all you need to do is see if the ball is up where it belongs. Although I have the oxymizers I have never found that they help reduce the amount of O2 you need to use. The flow meter has a high and a low scale, supposedly you can use the low scale if you use the oxymizer. Whenever I used to do that, my pulse oximeter would tell me I needed to use more O2, so I just use the high scale, which is for non-oxymizer cannulas. Every time I bring that up a couple of people say, no, theirs works great, so maybe they work for some people but not for me. My VO2Max is pretty good though. I now use the mask only a handful of times every year. The problem with the mask is that, first, you need to be on a long flight, at least two hours, to justify the long climb to 19k+, and it probably needs to be a west to east flight because the winds almost always outdo the gain in TAS when you go the other direction. And second, the mask makes it difficult to eat or drink, so there you are, on a long flight and can't eat or drink. Not very convenient. If you get one, mine came with the mike in a vertical position and that did not work at all. I found I was able to bend the mike cable to a horizontal position several years ago, that works, and there it has stayed for about a decade. There is really no need to buy more than one mask, I seem to remember it was around $400, and the cannula works fine for passengers, just not legal for the pilot. The mask does help a little in preventing the nasal drying effect of a cannula. There is lots of capacity in the 115 c.f. tank as Paul K. said. There is really no need to go to the complication of a demand system. The free flow cannula system works great and plenty of duration. The mic'd mask works fine also, just the eating a drinking thing. On the other hand, I have found some really nifty speeds up in the 20k altitudes. Peoria to Fredrick, MD in 1 3/4 hrs. Williston to Minneapolis in an hour and a half. Those are the trips where you might see ground speeds in the neighborhood of 300 kts. in a measly old 231, while sipping fuel.

It is a myth that removing the vacuum system saves weight. Every panel change I have made towards more glass and less old-style instrumentation has gone the other way, not big changes, but you lose a few pounds of useful load every time. The 231 has a single 12 volt battery. You should not think of it as any kind of a backup at all. If you switch the master off and look for a place to land you should drop the gear while you still have current, and fly gear down, you likely will not have enough juice to drop the gear at your point of intended landing. You might have enough juice to use radios when you land and you might not. Been there done that. I personally would not rely on a half hour internal backup to get me home either. There are many places I have flown, mostly out west and over mountains, where a half hour would not be sufficient, especially if you happen to be in the flight levels when the problem starts. It takes awhile just to get down if you mean to avoid Vne. Been there done that also. I had to do an emergency landing from 19k in Canada, from about 20 miles out from an emergency airport once upon a time. We had not been in IMC for the previous two hours, but got pushed by tailwinds into the back side of a system and 7000 feet of the descent was VMC. I would not have succeeded without fully functioning instruments. In the 231, with its ability to travel high and far, you will find yourself dealing with some kind of weather issue on every long trip. Personally, I decline to have any single point of failure instrument systems in my aircraft. If you want to get rid of the vacuum you need at a minimum, a backup alternator for the electrical, and because of the virtual shutdown of the FSDO’s that is really hard to get right now. If you install a dual reversionary 275 system you need a third AI of a different technology, say an RC Allen electrical gyro. One of the members of the forum had a failure of some kind put red X’s on both 275’s just a few months ago. Garmin was looking into it. But I have not read that there is a fail safe resolution. The speculation is that loss of airspeed input caused the entire system to shut down. Don’t expect to gain useful load with the necessary instrumentation. I have one 275 as a backup to the vacuum instruments. If the FSDO ever approves the 337 for the backup alternator (it has been about a year now), I will remove the vacuum, put in the backup alternator, install the dual reversionary 275, and put an RC Allen AI over on the co-pilot side. I figure that all will run north of 12-13 AMUs and cost me another 10 pounds at least, but I am worth it. I fly many Angel Flight passengers and they are worth it. This may sound overly conservative, but as I have said, I have lost the alternator and all power, I have had the pleasure of descending from 19k through IMC over the Great Lakes. The 231 is a great machine, but you are helpless without robust and well backed up instruments. Just remember, lose your instruments and your remaining lifespan will be about 173 seconds.

Also check the wastegate. One difference between the Merlyn and the factory fixed wastegate is that the Merlyn can fully close. Perhaps it is not fully closing and you are wasting exhaust overboard. This would probably not be seen on the ground because there is no need for the wastegate to close.

The aircraft is not flying in the photo. The wings are folded, the left stabilizer and elevator are gone, and it is shuttlecocking into the ground. The aerodynamics in that photo have no relationship to the aerodynamics of a flying aircraft. Think of it as hanging from a string, with some upward drag because the wings are still attached although upward folded. Remember, there is a passenger and luggage in the back, upward drag on the wings about a center of drag that no longer has anything to do with the classic center of lift of a wing, and practically no upward drag at the tail. People keep trying to relate that image to classic, flying aircraft, aerodynamics. The aircraft is not flying. There is no lift from the no-longer-existing elevator, which is on a lawn two blocks away or working at arriving on that lawn.

Even the later avionics were not that good by today’s standards. The vacuum instruments are good. The pump needs to be replaced every 500 hours though. The KFC 200 autopilot is really good, certainly the more modern APs are better, but for the analog era the 200 is robust. The King Silver avionics are pretty much outdated now. If it has the original avionics yiou will probably need to spend quite a bit avionics, you need a good WAAS GPS at a minimum.

Aside from issues with the data, the rounding effect or whatever you want to call it, will distort climb and descent rates over altitude changes of a few hundred feet, which is what we are talking about with this incident. Here is a simple example. The transponder reports in increments of 100 feet so it necessarily rounds up or down at some point. Let’s say it does that at 50 feet. So if you are flying at 3040 the transponder reports 3000 (setting aside the pressure altitude issue for the moment). At 3060 feet it reports 3100, so it says you have ascended 100 feet between the two ADSB broadcast although the actual altitude change was just 20 feet. The maximum distortion is about 200 feet of altitude. Say you start at 3040 and ascend to 3160. You would ascend 120 feet but ADSB would report 300. My simple example is just to explain the rounding effect, but it is more prevalent in real life flying and not as clean as in my example. I flew with an MX20 for many years that reported encoder altitude, altered for local pressure. It was always off and in weird amounts. If you are climbing or descending, say, 10,000 feet the potential distortion is still only 200 feet so percentage-wise it is small. But if you are going from 3000 to 3100 the distortion can be substantial. I did a tour of an ATC facility years ago. They told us they are aware of these issues and do not pay attention to reported altitude changes of less than 200 feet. As I said in my earlier post there is no doubt there was a significant altitude and speed change in this instance. I am just saying we can’t use that data at the granular level we would like because it is just not that accurate. Also, I would like to see the actual data and know how it was put together. I read the ADSB Exchange web page, it looks like the data is harvested by hobbyists with a Raspberry Pi, a Software Defined Radio and an antenna. I looked at sample data and it is not in the format that it is presented in the graphics in this thread, so at some point the actual data is translated. How, what choices are made? Are parts of the data from multiple harvesters put together into one data stream? Is it AGL, MSL, pressure compensated (it appears not to be)? I am not saying it is not useful, I would certainly not stake my life and fly my aircraft based on the data, not at this point. Notwithstanding, it is still interesting and it is data.

I was able to cure the coupler issue by going directly to Mooney for the part several years ago. The aftermarket couplers we tried, all failed in a very short time and one failed spectacularly when a non-MSC installed it, left out a bushing, and it fell off into the running engine. However, the Mooney supplied part has lasted for four or five years without incident. I want to say it was in the neighborhood of 3-3,500 but I was happy to use it because it worked. I am trying right now to get a 337 authorization to install a backup alternator but the FSDO has been sitting on the request for a year because of COVID. There is an alternator available by B&G. However, one of our members recently reported the failure of a dual reversionary G275 system, and the consensus conclusion seemed to be that the safest routes is to have attitude indicators of two different technologies, which means keeping the vacuum system and the King AI, and then installing a 275 (or another electric backup that is legal for primary as a turn coordinator). That is what I have right now. The other route would be to install the dual 275 system and add an RC Allen AI with a backup battery. It is also electric, but different method of operation. It is a moot point though, until the FSDO’s are actually back and running. We just had a fatal incident that may have been caused by disorientation in IMC, see the Minnesota Crash thread. Going with a system such as the dual reversionary 275 that has a single point of failure is out of the question for me.

What would you like to know? I can tell you that if you run the aircraft right, it is fast, sips fuel, and can travel incredible distances without a fuel stop. Minneapolis to Boulder, for example. It was Mooney’s first attempt at a turbocharged piston so there are some things that were improved in later models, but invariably at the expense of useful load.

We need to be careful about using public ADSB data to calculate anything other than very gross climb and descent rates, or to say whether the subject aircraft was in the clouds or just above. Remember some things about ADSB reporting. As I understand it, ADSB altitude comes from a blind encoder. The blind encoder uses 29.92 as its pressure reference, not the actual local pressure. ATC’s systems convert that to a pressure altitude. Our ADSB out units report in increments of 100 feet. Yesterday, because I was a little concerned about the accuracy of all this, I watched what my KT74 was reporting west of FCM. At one point it was flipping altitudes for several minutes from 2500 to 2600 and back on intervals of ten seconds or less, with no actual altitude changes going on except ground turbulence variances of maybe 20 feet or so. My actual pressure altitude at that point was 2800, not 2500. The ambient pressure was 30.22, so a difference of about .30 inches hmg from 29.92 and therefore the 300 feet. So the ADSB Exchange information that people have been using, is that recording altitude after it is translated to pressure altitude by the ATC system, or is it just reporting what comes out of the transponder, which is generally several hundred feet different from pressure altitude? I looked at their website and it says the data is not FAA data, it comes from a web of all kinds of harvesters, including amateur harvesters. They are very proud of that. For our purposes, that virtually guarantees that it is data not translated to pressure altitude, so it does not represent the actual altitude that the aircraft was flying at. There is no doubt that there was a high descent rate in the last seconds of flight. There is no doubt that the pilot went through the cloud deck. But reading the ADSB data to suggest the pilot was dipping in and out of the clouds or constantly climbing and descending prior to the final turn, just misunderstands the nature of the data. The data is not accurate enough to tell us those things.

To answer your question, I personally am concerned about the cumulative effects to the point where almost all of my weekend, keep-in-practice flying consists of flying approaches in VMC. I fly them about 30% on the AP and about 70% by hand. All kinds, ILS, RNAV, VOR, I used to even fly NDBs but got rid of the ADF about a year ago, there aren’t any NDB’s around here anymore. The first thing I do when the plane comes out of annual during the winter is spend about a month practicing like that, and getting myself approach hardened again. But the AP is still safer.

+1 on the 510, and if you happen to have a second, older GNS 530/430, installing the 210 with that unit will not do what you want. I tried that. The GTN and GNS series will crosstalk, but only up to a point, so the stuff you want to display on your iPad would be fed into the GTN but not fed from there to the GNS, to which the 210 is wired. At least that is how it happens - or does not happen - on my panel. I think you can get ADAHRS from the 210 because that is generated inside the 210, but not traffic or other ADSB, which is fed from the 345 to the GTN.

Great lesson in Skew T Scott, thank you.

For those looking for the ATC tapes, I found both the Minnie Approach tape and the FCM tower tape on LiveATC.net. To listen to the Minnie Apch tape, click on the archive link, chose Aug. 7, chose 2230Z and in the line that displays feeds, scroll way down until you find KMSP Approach 121.2 . As I told someone in a PM, that is the alternate approach frequency to 134.7. You will hear the communications with 9156Z starting at about 28:29 on the tape. Unfortunately, it does not appear that we can get anything other than very approximate times from the tapes - off by minutes. The approach tape is stated to be from 2230-2300, for example, but the recording starts at 32:04 and counts down from there, so it is longer than 30 minutes. It is impossible to know if it starts at 2230 on the button or a couple of minutes later. The same with the tower tape, the times are only very approximate. The content is about what would be expected and confirms what the NTSB rep said in his interview. At 28:29 on the tape, which is roughly 17:32 Z, he clears 9156Z direct to ZAMUD to join the final approach course. At 27:45, roughly 1:45 later he says 56Z descend and maintain 3000, cleared the 10 Right ILS approach. About 4:15 later, at 23:28 on the tape, he instructs 56Z to go over to tower 119.15 . None of the pilots responses are on the archive. The tower tape then starts and has the same kinds of time problems. The animated recording very early in this thread appears fairly accurate, although missing some tower communications. At 23:16 on the tape, which is roughly 36:44Z, the pilot checks in: “Flying Cloud Tower, Mooney 9156 Zulu with you. The tower responds with a clearance to land on 10R. At roughly 22:37:10 tower says Mooney 9156Z 10R cleared to land.” Pilot does not respond. Tower calls 9156Z 15 seconds later and the pilot says, Yeah go ahead. Tower again clears him to land on 10R and says altitude indicates 2700, pilot responds “Roger.” There are at least two more tower calls after that with no response. Listening to the tower tape, I have to say that the pilot did not sound distracted, his responses were pretty much immediate except for one call and he did not sound confused. He sound like a pilot who did not understand he needed to repeat clearances as given and that is all. Let me repeat, these times are off by minutes. The hand off from approach on the approach tape appears to be 17:38:36Z but the pilot’s first contact with tower is 17:36:44 on tower tape, which is two minutes before the handoff on the approach tape, so the times are only a very rough guide. We know that he was cleared direct ZAMUD, told to descend and maintain 3000, cleared the ILS 10R into Flying Cloud, handed to tower, cleared to land by tower, and tower noted his altitude at 2700 at one point. All these match with the ADSB track into the S turns, except the times are just very rough. If anyone has a better way of establishing times of the calls, have at it.

@Scott Dennstaedt, PhD I have a question while you are here. I watched one of your videos on Skew T Log P within the last month. I had always thought that the cloud tops would be where the temp and dew point lines separate. However, in the video you were describing how, at least in some circumstances, the lines could stay pinched together within a few degrees after they separate, and clouds would be possible in that area. I went back and looked at the RAOB you posted and saw that the lines did do that up to around 5,000, although as you said in your post at the time, I believe, there was a temp inversion that would cap the clouds where the lines separated. I do see in the RAOB that the temp line takes a small but abrupt jog to the right where the lines separate, meaning the temp increases a few degrees. Is there are chance that cloud tops could have gone further up the graph to where the lines started to divert further at around 5k, or is that small temp increase enough to cap the clouds?

I went back and checked Scott's post. It is on page 10 of this thread. He says: "... there was a RAOB taken pretty close to the time and location of the site of the crash. This shows the bases of this stratocumulus deck were ~1200 ft AGL and tops were ~2700 ft MSL; so the clouds were less 1,000 feet deep. The sky was overcast which is also seen on the IR satellite imagery. So an instrument approach would be necessary given the weather at FCM." FCM is at 906 so 1200 ft AGL is 2100 MSL and the tops were 2700 ft MSL, thus the deck was 600' thick. Now, that was at FCM, not at Victoria, but they are only about 15 miles apart, or maybe a little less. The NTSB rep says in his statement that the wx at FCM at the time of the accident was 1100 OVC, so that would be a 700 foot deck, assuming tops at 2700. Not significantly different from Scott's report. The NTSB rep did not state tops.

I agree with what you say 1980mooney, it was the left stab and elev that were missing. I don’t see any significant pieces left in the crash video or photos. However, the NTSB rep says unequivocally in the interview, twice, that the aircraft was uncontrollable after departure of the stab. I don’t agree with your thesis that there was some kind of control, the NTSB says there was not.

I feel that flying an approach on autopilot actually is safer. However, I have had enough quirky things happen with the GPS + GPSS + analog AP system to know the importance of constantly checking that what you think you have commanded is what the system is actually doing. The biggest challenge is when something happens that requires flying by hand on a moment’s notice, or resetting a procedure on the GPS. So I practice both. A major issue, I think, is that these are not cohesive systems, they are separate components made by separate manufacturers and added in over time. No one, to my knowledge, has written a manual that says how the overall system is going to work. The pilot needs to intimately understand the quirks of each of them.

I have to correct one thing. I stated that there was an engine monitor on board. There was a dial-type JPI in a panel picture when the aircraft was sold. It is in a picture on aircraft.com. However, I reviewed the panel photos in the Kathryn’s Report and there is a blank where that JPI is in the other panel picture, so I cannot verify whether there was a JPI or another monitor. I don’t know which photo was taken when. However, the NTSB rep says in the Kathyrn’s Report interview that they have engine data that they will review.

There is quite a bit of factual information, see the Minnesota Crash thread. The NTSB has stated that the aircraft was on an instrument flight plan from AXN to FCM, and was on the ILS 10R into FCM. See the NTSB interview in the Kathryn’s report. At page 10 of the Minnesota Crash thread is a graphic by 1980mooney using ADSB data and showing the flight path. The aircraft was inside the intermediate fix, ZAMUD, at an altitude of 3000-3100 and slightly left of course. Intercept altitude for the approach is 2700 and at ZAMUD the pilot is supposed to descend to 2600 at STUBR, which is the FAF, which is at that point roughly three miles away. The plotted course data shows that the pilot turned southbound and descended to 2600-2700. This would suggest he was correcting to get on the final approach and at the correct altitude at STUBR to intercept the glideslope. At the end of the southbound turn, the aircraft turns abruptly northbound and altitude variations begin. The plane at that point is 7-11 seconds from impact. The descent rates from that point to impact were very high. There was a cloud deck about a thousand feet thick, from about 2700 to around 1100 or 1200, according to a recent RAOB. The ATC record suggests the pilot was either distracted or impaired, as his responses to tower were delayed and nonstandard. One side of the horizontal stabilizer and elevator departed the aircraft. The wings folded in the positive direction. The aircraft fell to the ground uncontrolled in a shuttlecock descent. Two separate eyewitnesses said that the wings folded in the air and the aircraft spiraled to the ground. The two wings were found on the ground essentially intact except torn off at the roots. There was no damage to the right wingtip, indicating the aircraft did not tip to the right and impact right wing first. It pancaked. The stabilizer and elevator were found two blocks further back on the flight path. These things are uncomfortable, certainly, but they are in the record. It would be good to get time-stamped information for the communications from tower, and the communications with approach before that. It would be good to know the engine data, was it running and how fast, which the NTSB will tell us. There was an engine monitor onboard, which the NTSB says they have. It would be good to know the state of the AP, whether engaged or disengaged and in what mode. It would be good to know whether there was an incipient gyro failure. The state of the AP, the vacuum pump, and the gyro we may never know because of the fire.

Exactly.

This is starting to make a little sense to me in light of information provided by the NTSB. According to the NTSB the aircraft was on an instrument flight plan and was on the ILS 10R into flying cloud. If you look up this thread to about page ten, 1980Mooney puts up an ADSB graphic with two waypoints, ZAMUD and ZIGCO. His post was considering whether there was some confusion between the two RNAV’s into 10R and 10L, but we know now that the aircraft was on the ILS, not either RNAV. What is signficant about his graphic is the it shows the location of ZAMUD on the pilot’s actual route of flight. ZAMUD is the intermediate fix for the ILS 10R. The accident site is after ZAMUD. At ZAMUD the pilot is supposed to descend from 2700 to make 2600 at the final approach fix, which is STUBR. At ZAMUD the aircraft was at 3000-3100 or about 400 feet higher than the 2700 intercept altitude. This would not be unusual if the pilot is being vectored onto the approach, he might have been cleared to maintain 3000 until established, for example. For whatever reason, the aircraft deviated slightly left of course after ZAMUD, so he would have found himself around 3 miles from STUBR, around 400 feet too high and left of course, and he would have needed to cure the altitude problem, in particular, in order to get on the ILS downslope. It was at that point he turned right (south) and descended. He got to 2600 at one point, which is the altitude he needed to be flying at STUBR but was slightly higher at 2700 at the end of the southbound turn. Altitude was still relatively stable at that point. It was at that point that things went wrong very quickly. at 17:39:39 the aircraft turned north and after a couple of more seconds, began to descend further. It was now northbound, away from the approach course and toward the impact site. From there until impact was in the vicinity of 7-11 seconds There are several possibilities. There could have been a vacuum or gyro failure. I have had both, and neither one happens in 10 seconds in a vacuum operated gyro. The gyro would not have been working well, but if it tumbled at that exact point there would have been symptoms and altitude variations before then. Another possibility is a failure in the autopilot control panel. As an example, my AP is a KFC200. It has an Up/Down button. If the AP is in Alt Hold mode, pressing the down button will cause a descent at about 700 fpm until the pilot takes his finger off the button and then the AP holds the new altitude. I use this in just this situation, with a thousand feet or less to lose and a reason to hold altitude thereafter. This spring, this function failed. The Up/Dn button acted as a trim control, pressing the Dn button would continuously run the trim down and then hold the down trim rather than a new altitude, when the button was released. I discovered it during VFR practice approaches and got it fixed. The pilot also may have, either intentionally or inadvertently, disengaged the AP. The AP can be inadvertently disengaged by simply using the trim button on the yoke, which the pilot might have done in order to change trim and get down to the desired altitude. If the AP remains engaged and in Alt Hold mode but for some reason is losing or gaining altitude, and the pilot tries to correct with pressure on the yoke, the effort will work for awhile, but the AP will run the trim to counteract that pressure and the pilot finds himself working directly against the AP and needing to disengage to fix it. At about the point where the southbound turn began, the pilot would need to dial the inbound course in with the course needle and switch to APCH mode on the autopilot. If he switched but had inadvertently failed to dial in the correct inbound course, the aircraft would immediately turn to find that incorrect course, which could explain the sudden northbound turn. The pilot would respond by disengaging the AP and hand flying, and making that transition with no notice is difficult. These are all possibilities and there are certainly others. What is significant is that the plane was stable and on the approach until just prior to the FAF when the pilot would have needed to correct course and lose altitude quickly. Then something happened.

If you look at the specifications in the listing on aircraft.com when the aircraft was sold, it had both backup alternators and a standby vac, so the pilot had resources if the vac failed. https://www.aircraft.com/aircraft/1207543/n9156z-1991-mooney-m20m-bravo The panel photos do not show a backup AI, but there was a Turn Coordinator. My own experience with failure of the vac is that the AI continues to work for awhile, but you really need to disconnect immediately if it is failing because the gyro falls slowly and gives false readings as it does, then when it starts to wobble you have a real problem if you are on AP still. If the 256 itself fails, the failure in my own experience is very slow, over more than one flight, and although the aircraft might not maintain the final approach course very well you would be able to penetrate a deck that thin. You might be off course, but you would get through it. All that said, there might be a sudden failure mode of the 256 that I am not familiar with. I agree with Don, there is no excuse now for not having a good, backup, electric AI. Among other things, if the primary AI is drifting off and showing, for example, a bank when the aircraft is not in a bank, that would be immediately apparent by looking at the backup. If the vac fails it is critical to either immediately switch to the backup vac if you have one, and if you don't, get the aircraft off AP, hand fly, and go to what instruments you have available and that are working.

In connection with the "Minnesota Crash" thread I searched for prior incidents involving folding of the Mooney wing. I found three, a Mite, a J and the Rocket incident referred to earlier in this thread. If you want to see the references, look at the other thread. Now there is a fourth, the Bravo that went down in Victoria MN. I found another brief reference to a J incident, but there was not enough information to determine whether it was the one I had already found, or a second J. I exclude the Mite from this discussion because the wing construction was different. What was interesting from a forensic point of view about the prior two modern Mooney incidents was that the wings had failed in a negative direction. I tried to explain my understanding of what "negative" and "positive" lift mean to aerodynamics experts and I think I did not do a very good job in the other thread. It is pretty simple. As I understand it, "negative" lift or failure of the spar in the negative direction means toward the belly of the aircraft, regardless of whether the belly is up or down with respect to the earth. "Positive" lift or failure is towards the ceiling of the aircraft, again, regardless of the aircraft's orientation to the earth. As we know, the wing of our normal category aircraft is certified to sustain positive loads a little more than double the certified negative loads. That out of the way, the explanation of the Rocket failure was particularly clear in the NTSB report. Mooney had done an analysis and concluded that the aircraft flipped in the air and the wings failed in the negative direction. The J report was not quite as clear, but the same failure, in the negative direction. The recent Bravo was the only modern Mooney inflight spar failure that I found, where the wing(s) failed in the positive direction. I know that there was the "artifact" discussion that posited that the tail struck first, then the right wing, and that somehow caused both wings to fold up. I personally think that was a useful discussion even though I disagreed with the theory. However, more than one witness description is now available saying the wings folded in the air. There is video evidence of the right wing after the crash, intact and undamaged at the wing tip. The NTSB says the horizontal stab and elevator departed the aircraft before impact and rendered the aircraft uncontrollable. I think we have all concluded that the wings folded before impact. We have all been cognizant, if not proud, of the strength of the Mooney wing. These incidents, however, show that we need to be more cognizant of the vulnerability of the horizontal stabilizer and elevator. If there is a flutter failure and the stabilizer departs the aircraft, there will be an abrupt nose-up or nose-down of the aircraft (depending on what direction the wing is generating lift at that moment) that can fail the wing because of the abrupt change in angle of attack. This does not require a sharp pull up by the pilot, it only requires departure of the stabilizer. In my mind the two, a sharp pull up and departure of the stabilizer are not related. Failure of an aerodynamic surface due to an excessive pull-up is a function of knots indicated, angle of attack, lift generated, and the lift capacity of the surface. Failure of an aerodynamic surface in flutter is a function of true airspeed, stiffness of the structure, and harmonics. The stab can be ripped off by flutter regardless of the lift load on the stab or on the wing, or whether there is a lift load on the stab. The point is that as much as we value the strength of the wing, we need to be very cognizant of Vne and the consequences of exceeding it. Someone said, in the Minnesota Crash thread, that the critical speed for flutter in our airframe is 241 knots. That is not much of a margin over the 195 Vne if you have allowed the slippery airframe to enter an uncontrolled dive in IMC. The information gathered in that thread indicates that the departure from a relatively stable altitude to the moment of impact was between 7 and 11 seconds. Also, if the stabilizer departs the aircraft, it is not particularly relevant whether the wing survived or not, the aircraft is not controllable.

The simple answer is that if you are really 55% LOP and want to increase to 60%, the best way to do it in the 231 is to increase MP until the fuel flow is 9.2 - or so. Fuel flow is not stable to the tenth, at least not in my aircraft, so if it is varying a couple of tenths, but varying around 9.2, you should be good. As you already know, the 231 is unique even among turbo aircraft in that when you change the MP, the fuel flow changes with it trying to keep the same fuel/air ratio. That mechanism isn’t perfect, but you have two things going for you in the change you propose. First, what you propose is not a big MP move so although the fuel/air ratio may not be exactly the same, it will be pretty close. Second, as long as you operate under 65% HP the GAMI people and Mike Busch both tell us that we can’t hurt the engine. so as long as the engine is happy (not running rough) you are not hurting anything at that power setting.