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Emergency Landing - Comments and Questions

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So, a little backstory. I am sure some of you will remember my post where I was testing the RTH function when the battery reaches a critically low level and the RTH function is triggered. I learned that it is a situation you want to avoid or there is as good chance you, or more appropriately, your 520, will be screwed. My test resulted in loss of control, due to my false belief that the RTH function can be aborted by any control input, which will bring the 520 to a hover if you immediately release whatever input you gave the 520. I am not sure how I came to believe this but it doesn't work, as I found out. Short story is the 520 responded erratically to my control inputs until it made contact with the roof of my house, rolled down the "V" where 2 roof lines intersect, and contact the sidewalk, inflicting serious bodily injury to the 520 and the E90 camera. I have worked on the 520 a few times and felt comfortable repairing the 520. Initially I thought the camera was not damaged save for the UV lens that shattered while protecting the camera lens. If you are flying without a UV lens or otherwise protecting the camera lens I would respectfully suggest you reconsider. With the 520 repaired I realized that the camera would not function normally and soon figured it had some more serious issues than a shattered UV lens. The camera was sent to JOhn at Yuneec Skins who farmed it out to a very talented person who had the knowledge and expertise to return it to like new condition save for a few cosmetic scuff marks.

Fast forward to mid September in Vermont. The fall foliage colors were busting out all over and a friend of mine and I decided to do some flying on a beautiful clear, sunny day. He also flies a 520. I had flown the 520 a few times since I had got it flight worthy so I was looking forward to having some fun getting pictures of the changing fall colors. We alternated flying our drones. Upon returning to land on my second flight I noticed that the right landing skid did not come down when I lowered the gear. I cycled the landing switch. I don't recall if the right side came down until the second or third attempt.I turned the 520 over and cycled the gear several times. Each time it performed as expected.

Returning to land upon completion of the next flight the right side again would not lower and cycling the gear several times did not cause the right side to get with the program. It now became a question of getting the 520 on the ground with only the left gear lowered. I gave Larry the controller and he flew the 520 low enough for me to grab the lowered left strut. At that point Larry attempted to shut down the prop motors but was unable to do it regardless of what he tried. Ultimately, believe it or not, Larry set the controller down, I held onto the left strut, and he reached in from below and popped out the battery. When we flipped the 520 over the gear would recycle properly as many times as I tested it. Wondering if there was some unidentified damage from the roof encounter, I replaced the right landing gear mechanism. I flew the 520 a few times subsequently with no issues, until 2 days ago. The weather was beautiful and I decided to get some pictures of the neighborhood and the lake. The first flight was uneventful from a pilot point of view. The second flight appeared to go equally as well, until I returned for landing and realized the right landing strut would not come down.

I was able to get my wife's attention as she had just gone inside. When I tell her what I want her to do she thinks I have lost my marbles. Becky places the requested 55 gallon barrel that we keep in the garage to collect the water and soda bottles to be recycled at the end of the driveway. I flew the 520 with the left side of the gear retracted just over the top of the barrel and then attempted to descend into the barrel. The prop arms acted as the landing gear, contacting the rim of the barrel. The camera was protected inside the barrel. I left the video recording throughout the landing. The issue was that I was unable to shut down the prop motors. The power toggle was retarded completely as soon as the prop arms contacted the barrel rim. Additionally, I pressed the start/stop button. There was some bouncing around and I opted to fly the 520 off of the barrel. The same thing happened on the second attempt. I am not sure what I did differently the 3rd time but the props shut down. Incredibly, there was absolutely no damage to the 520 or the recently repaired E90. As before, when I turned over the 520 and cycled the gear, both sides worked properly the 10-12 times that I tested it. The offending right side is not getting hung up on anything.

So I am looking for comments on several fronts.
1. The landing gear mechanism is pretty simply. Contacts on the landing gear mechanism touch contacts within the body of the 520 and you are good to go. If the landing gear is properly positioned in the 520 the contact between the body and the landing mechanism is guaranteed. The gear worked properly since I replaced the right gear mechanism, including a flight immediately before the flight in question. Thus, I do not believe it is a power issue. Could this be a software issue? I have not done the recent update the popped up on my controller as that would be another variable - unless tis is a recognized problem and an update resolves it.

My other question revolves around the landing gear in general and how, or when, it functions. Can you shut the props down if the landing gear is up? A mechanism to prevent this from happening would be the easiest explanation for what I experienced. Typically when I land, I ****** the throttle completely when the skids are on the ground. The 520 shuts down pretty quickly. I do not use the red start/stop button to shut down. I thought that maybe with the gear up the props won's shut down by retarding the throttle but will if the start/stop button is depressed. I thought I did both actions pretty much simultaneously. My sense was that when I released back pressure on the throttle because it wasn't doing anything, the 520 started to fly without any power input. Unfortunately I have no idea what I did no the third attempt to get the props shut down.

Any input would be appreciated. Unfortunately, at this time I have a 520 that I consider unreliable. The 520 is a backup for drones on a technical rescue team and for the state USAR team that I am a member of. I have taken it off line as I do not consider it a dependable piece of equipment at this time.

Thanks for taking the time to read this and thanks in advance for your input. It is appreciated.

At least I got some pictures! The 520 "repositioned" itself after it shut down but you get the idea.
 

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That was a very tricky landing on the barrel.

Since you changed to another landing gear and had the same issue I am guessing that there is a mechanical issue with the landing gear receptacle on the right side of the aircraft. Since it works when the aircraft is inverted you have good contact in that position, but when upright something is out of place. I suggest you remove the upper and lower shell and do some probing of the aircraft side of the actuator connection. It could also be something at the circuit board for the landing gear. I don’t recall the exact position of that board in the H520/H Plus, but you can easily follow the wires.

When you tried shutting down with the motor arming switch, did you hold it in for a minimum of 3 seconds? When landing my Typhoon H on uneven ground it was reluctant to disarm the motors. I had to hold the switch in for at least 5 seconds. The motors would not throttle down in that situation either as the aircraft is trying to level itself.

To my knowledge the gear does not have to be down to disarm the motors in flight. Your friend is a brave man pulling the battery from an inverted, hex headed, blade style grass trimmer.
 
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I am curious if there is something in all the h's that is similar in the way they land,I'm sure it's way above my level of understanding,but, my H pro did the same thing about 3 weeks ago. I was practicing landing and rth. I don't remember what procedure I was using at the time,,,was in angle mode and could not control the drone very steady,,full throttle decided to hand catch and that went well ,but the red button would not shut the drone down.landing gear was working fine, So I managed to put down the transmitter and go for the sswitch which is on top of the drone. With my rather short arms this did not go well,and the drone trying to power away from me,I did get the transmitter in turtle mode before I set it down then with as big of an arm arch as I could manage I went for the swich,,. I got a slight brush from one of the props ,no injury at all then on the second try I found the switch button and got it to shut off immediately. I was wondering why it would not power off with red button on transmitter,I know I held it down but probably not long enough. I was a little distracted. Gonna try the red button again have had a few great flights and lots of fall color pictures since then. Your post and Dooms comments make me wonder,so I gonna do some tests. Don't know if I could hit that bucket though?
 
At that point Larry attempted to shut down the prop motors but was unable to do it....

The issue was that I was unable to shut down the prop motors. The power toggle was retarded completely as soon as the prop arms contacted the barrel rim. Additionally, I pressed the start/stop button.

....but the red button would not shut the drone down. I was wondering why it would not power off with red button on transmitter,I know I held it down but probably not long enough.

@ DoomMeister has already addressed some good points for @P Howard's landing gear. The failure of the red button could best be addressed by a quick review of the flight logs. If you guys will upload the flight logs and indicate the day and time of the flights with the red button issues, we can see what happened. See the appropriate Attachment in the PDF document attached to Way To Fix Drones project
Attachment 61 (Typhoon H Flight Log Retrieval)
Attachment 63 (Typhoon H Plus Flight Log Retrieval).
 
The mechanical yokes inside the retract mechanism may also be damaged. If it is not electrical you may want to remove the mechanism and disassemble to check it out.

In regards to the Low Battery RTH, I am pretty sure the 520 is the same as the Plus and upon the 3rd Low Battery warning (they come every 30 seconds - so one minute after the first) the aircraft will execute RTH - depending on where it is different things can occur. However to disable this RTH - toggle the flight Mode switch. For instance if you are in Angle Mode when it happens, toggle to Sport Mode and back and this will stop the RTH but you have the remainder of the next 30 second interval to get on the ground.

Finally, when hand catching a Plus or 520, you must make sure that the aircraft is held in the exact position it descended to - any attempt to move it laterally will cause it to spool up the motors in an attempt to hold position and you will have to hold the red kill switch for 3 seconds, other wise a typical hand landing works as it should but once it is fighting you - well you know what happens.

Here is an example of a hand catch and launch - note the time I spend holding the red button is about one second to kill the motors.

 
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Thanks for all the comments. Would everyone agree this is not likely a software problem?

Your friend is a brave man pulling the battery from an inverted, hex headed, blade style grass trimmer.

I guess I was not clear on what we did. I held the upright 520's left strut that was down while Larry reached up from below the 520 to pull the battery out. Upright or inverted, it was still a bit scary.

I shall open up the body and see if I can discern anything out of place or unusual.

the aircraft will execute RTH - depending on where it is different things can occur.
I can vouch with a high degree of confidence that the aircraft does only one thing - ascends to programmed altitude or remains above it if higher than the programmed altitude. As I have discussed in a previous thread, activation of RTL mode at low altitude, critical battery level can result in loss of power at altitude with devastating consequences. Interestingly, the Mavic does respond differently depending upon its actual altitude vs RTL altitude and distance from launch point when the command is initiated. Not so with the 520.

When you tried shutting down with the motor arming switch, did you hold it in for a minimum of 3 seconds?
I believe I did but I'll forward the ulog to you and you can tell me if I did or not?

In a normal landing I fully pull the throttle stick all the way back once the 520 is on the ground. The prop motors shut down within seconds. I don't think it is related to the retarded throttle. If you start the 520 but do not power up and take off, it will autonomously shut down after a few seconds. It recognizes it is still on the ground. In like fashion, can the 520 recognize when it has landed and institute a shutdown command. The red button would be an additional shut down mechanism. As I recall, you must use the red button to shut down a Typhoon H. After landing the prop motors will idle down but will not shut off until you do use the button. So the question is are there certain situations where the 520 motors will not automatically shutdown? There was no indication they were going to shutdown on the first two landing attempts. I think we need the logs reviewed to tell me exactly what I did. In this type of situation you revert to your training and things happen too fast to reliably remember what you did exactly and in what sequence.

I am also wondering what you folks would have done in a similar situation, flying alone but no barrel within reach. One of you folks know I would have given up some fingers before I let the camera contact the ground!!
 
I guess I was not clear on what we did. I held the upright 520's left strut that was down while Larry reached up from below the 520 to pull the battery out. Upright or inverted, it was still a bit scary.
I was trying to insert a little levity there. If you hold the 520 upside down it is a six bladed lawn trimmer. If it is upright like in a hand catch it would be an inverted lawn trimmer.

As I have discussed in a previous thread, activation of RTL mode at low altitude, critical battery level can result in loss of power at altitude with devastating consequences.
What @Ty Pilot was getting at in his post, was that toggling the Mode switch (not moving the control sticks) will cancel the RTL and resultant climb and give you 30 seconds to control the aircraft before it attempts another RTL, which you can cancel again by toggling the Mode switch. The final act would be a low power auto land that cannot be aborted by the pilot.

In a normal landing I fully pull the throttle stick all the way back once the 520 is on the ground. The prop motors shut down within seconds. I don't think it is related to the retarded throttle. If you start the 520 but do not power up and take off, it will autonomously shut down after a few seconds.
This is the normal behavior for the H520 and H Plus. Yes the H480 does require use of the motor arm/disarm switch to start/stop the motors.

You might want to check the position of the Rate slider to ensure it is in the rabbit position when the motors will not idle down. Having the Rate slider less than Rabbit position reduces the values sent to the aircraft from the controls. If you are in Turtle position the aircraft would only see the full throttle down position of the stick as about 3/5ths of the full travel thus preventing the idle down and shutoff.
I am also wondering what you folks would have done in a similar situation, flying alone but no barrel within reach. One of you folks know I would have given up some fingers before I let the camera contact the ground!!
If I was alone (which I usually am) I would have walked the aircraft into a bush trying to force an emergency shutdown of the motors. Props are relatively inexpensive to replace.

A final thought. Once you have hand caught by the left gear. Give the right gear a wiggle then release the aircraft and try cycling the gear again. You can probably make several attempts at that before the battery gets too low.
 
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. . . . So the question is are there certain situations where the 520 motors will not automatically shutdown? There was no indication they were going to shutdown on the first two landing attempts. I think we need the logs reviewed to tell me exactly what I did. In this type of situation you revert to your training and things happen too fast to reliably remember what you did exactly and in what sequence.
Yes, if after initial contact with the ground there is movement, the aircraft will still be in position holding mode just like it is in the air - even though it may be on the ground and this is when you see a tipping over. This was much more prevalent on the H than it is on the 520 or H Plus but I have seen I a time or two. When/if this happens, immediately add power, stabilize above the landing spot and try again.



I am also wondering what you folks would have done in a similar situation, flying alone but no barrel within reach.
I would have caught it by hand.

As I show in that video I posted, a hand catch is a viable and quite simple solution. I guess it comes from my RC days but when you have an aircraft with retractable landing gear, you can bet that sooner or later you may have a problem with the gear. For this reason I learned to; and still practice hand catches and hand launches. The trick to a successful hand catch is to make sure that once you grab the aircraft, it must not move at all, so that it will go into the land/idle sequence. If however it goes into the position holding sequence and throttles up, the same applies; add power, let go and try again.

If for any reason you cannot accomplish a smooth hand catch, the final solution is what I call a live kill. That is a three second hold of the red kill switch and the motors will stop in any situation - flying or not. This is something that I would only plan to do in an emergency.


As I have discussed in a previous thread, activation of RTL mode at low altitude, critical battery level can result in loss of power at altitude with devastating consequences. Interestingly, the Mavic does respond differently depending upon its actual altitude vs RTL altitude and distance from launch point when the command is initiated. Not so with the 520.

When I got my Plus about three and a half years ago I detailed everything that was different about the Plus (520) as related to the original Typhoon H. One of the things I stressed was that the low battery RTH was a condition to avoid at all costs because (as you noted) the aircraft does a high energy demand (full power climb) precisely at the wrong moment - when the battery is low. It took me about five flights intentionally letting this happen until I found out how to stop it. Flipping the flight mode switch does stop it immediately!

I also found that there was another way to stop a Low battery RTH but it is one I do not recommend, a press of the kill button for over a second stopped it also. But as discussed, pressing that button too long in-flight will stop the motors as well, so I did not recommend that as an option.
 
I have done hand catches before but …… I am a veterinary surgeon. With my luck you know what would happen if I pressed my luck. I did attempt to hand catch the first time the problem presented itself when flying with Larry as detailed in my original post. He flies both a H plus and a 520 so he is familiar with them. Yet he was unable to shut the props down. I thought I was holding it still but maybe not. What about being ready to grab a strut but not actually doing it until you hit the red button 3 times to shut down the props?

I wondered about trying to land on the one skid and the move the aircraft laterally towards the down skid, tipping the aircraft over. The props can easily be replaced. Was thinking it might save the camera. Fortunately didn’t get to point where I had to test my idea.

Too bad I didn’t see your post before I did the same battery test. It was painful.

I still have an H which I occasionally will fly. Do you have a list for review of all the differences you found between the H and 520?

Thanks for sharing your expertise

I am working on getting the logs posted.
 
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I work with my hands too so I am am very keen on understanding what the drone will do in all phases of a hand catch and get what you are saying. I realize it is a risky maneuver but I know the risks and feel I have an understanding of every possibility. For me, what I am looking for is: does the drone go into idle or does it think it is still flying? Recognizing this aspect immediately is key to a successful hand catch IMO.

I think trying to land on one skid might result in the aircraft spooling back up but I have never tried this, perhaps this should be on my to-do list?;)

I made a number of videos about the Plus, and in each I discuss what I found different between the H and the Plus. I know the 520 is slightly different from the Plus especially in the different Flight modes such as CCC and so on - but not sure how that compares to the 520. One thing I am sure of is that Yuneec made changes between models and for whatever reason did not document those changes as well as we would have hoped. ;)
 
I work with my hands too so I am am very keen on understanding what the drone will do in all phases of a hand catch and get what you are saying. I realize it is a risky maneuver but I know the risks and feel I have an understanding of every possibility. For me, what I am looking for is: does the drone go into idle or does it think it is still flying? Recognizing this aspect immediately is key to a successful hand catch IMO.

I think trying to land on one skid might result in the aircraft spooling back up but I have never tried this, perhaps this should be on my to-do list?;)

I made a number of videos about the Plus, and in each I discuss what I found different between the H and the Plus. I know the 520 is slightly different from the Plus especially in the different Flight modes such as CCC and so on - but not sure how that compares to the 520. One thing I am sure of is that Yuneec made changes between models and for whatever reason did not document those changes as well as we would have hoped. ;)
I am anxiously awaiting the video of your one skid landing because I am too big of a chicken to try it! I think they call it recognizing your limitations!!
 
I only recently got an H+ about 2 weeks ago. I have read through most of the posts here and thought about the hand catch idea as I had read them. For I have flown the Q500 for several years. I noticed that on my first flight with the H+ that I wasn't to happy about that top mounted power button. From many years hand catching the Q500 and shutting down with that bottom mounted power button is what I grown accustomed to. Does anyone have a good clear reason why Yuneec went to the top mounted power button?
 
It likely was because in most cases, when you turn the drone off you are standing next to, and therefore above - the drone. I have hand caught my Typhoons 100's of times and not once did I need access to the power button.
 
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Gary,

The motors get disarmed from the ST16S so no need to use the power button during a hand catch. Unless you are using a lanyard of some type to hold the ground station, it would be very awkward using the power button to disarm the motors anyway.

After some hairy landings in longer grass that hid uneven ground and made disarming the motors a bit unnerving, I started hand catching more often. I always do when the ground is dusty or sandy like at the beach to avoid getting that in the motors or the camera.
 
Gary,

The motors get disarmed from the ST16S so no need to use the power button during a hand catch. Unless you are using a lanyard of some type to hold the ground station, it would be very awkward using the power button to disarm the motors anyway.

After some hairy landings in longer grass that hid uneven ground and made disarming the motors a bit unnerving, I started hand catching more often. I always do when the ground is dusty or sandy like at the beach to avoid getting that in the motors or the camera.
I think you guys both missed the point. I posted this here(instead of a new thread) because other user could not shut down the motors properly. If such a situation would happen to me I would have the same problem. Motors may not shut down for whatever reason and if I did a hand catch, I would have to carefully reach around under the spinning props to hit that top mounted power button. So, for safety reasons I feel the bottom mounted power button should've stayed on the bottom. Maybe Yuneec had other reasons for moving it but we'll never know for they produce poor quality user manuals.
 
If you are ever in that “situation” I would suggest you not attempt to reach in and try to depress the power button. It is much safer to reach up from the bottom and pop the battery out.
 
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I am not positive about this, but I strongly suspect that the power button may be inoperative with the motors armed. Even when unarmed you have to hold it in until you hear the tones, release it, and then it starts powering down the aircraft. It is not like operating a contactor to remove power.
 
I think you guys both missed the point. I posted this here(instead of a new thread) because other user could not shut down the motors properly.

Sorry, but I think you have missed the point. ;)

There is a sequence for hand catching and simple shutdown - I show it clearly in the video. I also outlined above that at ANY point during a hand catch, if the motors do NOT spool down - the hand catch (the hand 'catcher' in fact) has failed, and the only recourse is to let go, re-establish stable hover and try again.

At NO point would I advise to continue in such a situation OR attempt to power off the aircraft.

Hand catching requires the pilot have this sequence for 'Go - No Go' ingrained in their mind. If for any reason a hand catch can NOT be established correctly the pilot then must accept one of two outcomes: a possibly damaged aircraft OR possible injury to the pilot. In that scenario, I value my fingers, hands and face way more than the replacement cost of ANY drone.


Simply put: I do not accept a situation where I am fighting the drone with one hand as a viable option to anything . . . . . and I would never let myself get caught it that situation.
If such a situation would happen to me I would have the same problem. Motors may not shut down for whatever reason and if I did a hand catch, I would have to carefully reach around under the spinning props to hit that top mounted power button.

. . . . however it appears that you will accept that risk.

To put it into perspective; what I have outlined is, in the drone world what a 'go around' is to manned aviation. It is something that is ingrained into pilots - to know when to NOT push a bad situation and to simply pull up and start over.

What you are asking is the equivalent of: 'how can I be in the middle of a botched landing and just continue'? My answer is 'you cannot'. And even if you had a power 'Off' button conveniently located - I would still say you are accepting a risk and would advise that you learn how to hand catch correctly as well as how to 'go around' over all other options.
 
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Motors may not shut down for whatever reason . . . .
One last point :cool:

The motors WILL go to idle and shut down. . . . when you perform the hand catch correctly. I think that training to hand catch properly as opposed to, training to recover from a botched and very dangerous situation, is the way forward. As I said I have hand caught many different drones well over 100 times and once you learn the landing and shutdown procedure that each drone has: the hand catch becomes a viable option.
 
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One last point :cool:

The motors WILL go to idle and shut down. . . . when you perform the hand catch correctly. I think that training to hand catch properly as opposed to, training to recover from a botched and very dangerous situation, is the way forward. As I said I have hand caught many different drones well over 100 times and once you learn the landing and shutdown procedure that each drone has: the hand catch becomes a viable option.
This is very well addressed by you and your years of experience with the H/H+. My experience is solely with the Q500 and the H+ is a whole new and different beast to me and what I've learned from the Q500. Having only done 2 short flights with my H+, I've got much to learn about the proper/safe way of doing things with it. Do not get wrong, but, I do appreciate all the time that various experienced users take to write responses to my questions. As new new user to the H+, I hope to have many good years of flying with it and value your comments.
 
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