How it came about
This page is especially about my sample of the HIROBO Schweizer 300 and its specific features. Of course, general information about this model is given as well.
To my own surprise, I finally got the hang of nose-in hovering in 2017. Now I wanted to own a "real" model helicopter, not only micros. It should be even quite big and heavy, have an electric motor, and be "scale", so not for aerobatics – sort of appropriate to my age.
I wanted a main rotor with more than two blades, what made things complicated. A model of the Hughes 500 would have been to my liking, but there were only fiberglass bodies and five-blade rotors by different special manufacturers. To find suitable ones and fit them to a standard "broomstick" heli as a basis was too difficult for me and quite expensive.
In the Internet, or web for that matter, I found this model for which a three-blade main rotor is available from its manufacturer HIROBO. Besides, TMRF Rüdiger Feil, expert and distributor for HIROBO in Germany, makes an electric conversion kit. That seemed convenient to me, the more so as a few modelers reported success with this combination in German web forums. And the Hughes or Schweizer 300 has always appealed to me.
On the kit box is printed "30 class scale helicopter", and that's correct. HIROBO had brought out this model as early as 1995 and didn't modify it ever since. Back then there were only glow engines, and a .30 (5 ccm) was the standard size for sports and trainer helicopters. HIROBO's advertising claims that more than half of all model heli pilots worldwide have learned to fly with a HIROBO Shuttle. That may be even true, particularly since the model has been sold since 1985. Anyway, probably they derived this S-300 from the old Shuttle and both have several parts in common.
That should also pertain to the main rotor – as usual back then a two-blader with flybar (paddles) and mechanical mixers to the swashplate. On the main frame are mechanical mixers actuating the swashplate by means of three "standard size" servos. The tail rotor is driven by bevel gears and shafts – an advantage for me since I just dislike belt drives.
Nowadays, a 1244 mm diameter rotor (2000 rpm maximum speed), with blades exactly 550 mm long, would characterize a 550 class helicopter with typically 2.8 kg weight. KYOSHO specifies 3.2 kg weight already for the classic-design S-300, but a version with three-blade main rotor and electric motor will be even heavier (rather 4 kg). Adequately, .46 (7.5 ccm) glow engines are often preferred or today a powerful electric motor with up to 2 kW power and a 6s LiPo battery.
How long the three-blade rotor has been available is not known to me, but it is a well-made rigid all-metal rotor head with wooden blades – classic like the whole heli. Its diameter is 1092 mm (blades 477 mm long) and it should be operated at speeds between 1500 and 1800 rpm so it will need quite some power. As per Rüdiger Feil, who is a well-known competition flier (and "heli guru"), the model flies quite well even "conventionally" (with a gyro for the tail rotor only), but HIROBO recommends a "commercially available 3-axis gyro" nonetheless. The model is not capable of doing aerobatics, due to the mere fact that the main rotor blades have cambered airfoil and positive incidence angles only.
That "scale" on the kit box may be not completely true, considering the two-blade main rotor, but otherwise the HIROBO S-300 looks as true to the original as hardly any other S-300 model. The three-blade rotor is even closer to the original, even if it needs to have a more massive head and wider blades. So all could be fine and dandy if I wouldn't always find fault with something – see next section.
Though the kit box pictured above with its print and box art has been left unchanged since 1995, this box contained all the modern parts I had actually ordered (three-blade main rotor, electric conversion kit) and not any old dispensable parts (for a two-blade main rotor or a glow engine). All were neatly put together and packed by TMRF Rüdiger Feil. Included were instruction manuals for the basic kit version and for the optional three-blade rotor, as well as a few sheets about electric conversion. The instructions (text in Japanese and English) are unusually comprehensive and correct. All required data can be found, even if not exactly easily due to the manuals' sheer size. Searchable electronic versions (PDF) can be downloaded from the HIROBO website, though.
The instructions should, or better must be carefully perused and collated, and there are several things in the three-blade rotor manual overriding directives in the basic manual. Of course, there are no suggestions for modifications, but with some effort it's well possible to discern how to modify something. I wanted to reverse the main rotor's sense of rotation since, as supplied, it's "the wrong way round". With active support by Rüdiger Feil, the necessary modifications basically worked out, albeit without warranty to work properly. The risk was worth it to me, though, the more so as the modifications can be undone (even if with some effort).
Only a build thread in a German web forum drew my attention to the "problem": the horizontal stabilizer, which is slanted up by 30°, is blown by the tail rotor. In hover flight, that makes for turbulence and prevents the helicopter from standing still in the air. As a remedy, someone suggested and tried to install the horizontal stab really horizontally, or level, and that helped it. That goes against the grain for me, though, so I perused the instructions in search of the reason why a problem like that can occur on a scale heli. Soon enough this reason was clear, just trying to provide a remedy became quite a project then.
The HIROBO Shuttle's configuration, with a glow engine turning clockwise down in the main frame, makes for a main rotor turning clockwise (seen from above) as well. Like on any full-scale helicopter, the tail rotor is accordingly attached to the tail boom's right side. This way it blows outwards, away from boom and stabilizers. That's how it is on the HIROBO Lama, the other scale heli derived from the Shuttle (and which is said to be sold in far bigger numbers than the S-300), and there it is true to original.
But the original S-300's main rotor is turning counterclockwise and its tail rotor sits on the tail boom's left side. Its sense of rotation is not noticeable in flight so it's irrelevant, but on the model it should be at least on the same side as on the original. So HIROBO just put it on the left side where it blows at the tail boom and the horizontal stabilizer, for it must blow to the right if the main rotor turns right (clockwise). In this case the whole helicopter sways to the right, by the way, and in a full-scale heli the pilot sits usually in the right seat, perhaps because he can better look down from there. But both the Hughes 300 and 500, with their main rotors turning left (counterclockwise), sway to the left and their pilot's seat is on the left side.
So HIROBO tricked or wangled a bit to let the model look like the original without having to redesign major parts of it and produce variants. We wouldn't pay for that, either, but I would call the model only semi-scale. Now my bold idea was that a major redesign wouldn't be necessary anymore since brushless electric motors can easily turn counterclockwise. But notoriously the devil is in the detail so it (or he?) had to be tracked down and banished.
The rotor head is symmetrical but the blade airfoil is not – it is cambered (something like a NACA 2415). As Rüdiger Feil could confide to me, that's not a problem. The three-blade rotor had been originally created for HIROBO's CH-46 and CH-47 models, that is for counter-rotating tandem rotors. Hence I could simply order a set of counterclockwise blades. The rotor head's blade holders are just turned so their pitch arms point in rotation direction (shown for clockwise in the picture).
Of course, the freewheel (aka autorotation clutch) has to be reversed. According to this spare parts drawing, that should be possible but – with my tools and skills – I was not even able to dismantle the shrink-mounted parts (0402-016) and wouldn't have been able to re-mount them, either. Rüdiger Feil did that for me in his workshop.
The pinion has a threaded stub by which it is screwed into a clamping sleeve for the motor's shaft journal. Maybe both parts are available as different variants (cog modulus, shaft diameter) and that's why they are separate parts screwed together, or the pinion is simply the original one from the kit. However, a motor turning clockwise matches a right-hand thread while a motor turning counterclockwise would unscrew it. Because of that, I not only dripped Loctite into it but also drilled through and dowelled it.
If the main rotor's sense of rotation is reversed, the tail rotor's is reversed as well. The tail blade holders are not symmetrical so they can't be flipped over like those on the main rotor. That's not so bad, though, because the tail rotor is rigid and has no cyclic pitch control.
Still I had another bold idea: Perhaps it is possible to turn the bevel wheel on the tail rotor shaft ("2nd shaft") and put it on the other side of the bevel wheel on the drive shaft ("1st shaft") like drawn in here – the sense of rotation would be retained unchanged then.
For good measure, another wangle would be corrected: Because the tail rotor had been relocated to the left side (compared to their basic scale kit), HIROBO had to change the tail pitch lever's neutral position by 30°. Only this way the tail rotor blades have the incidence angle they need to blow to the right, to the tail gear. Geometrically, this is not exactly a good arrangement but just another necessary wangle. If the tail rotor' sense of rotation could be retained, the tail rotor blades would now have the opposite angle of incidence and the lever would be in the position actually intended – like on the HIROBO Lama (right picture) where all is correct.
Not even Rüdiger Feil could help here, that is he couldn't relocate the bevel wheel because it is made from plastic and injection-molded directly onto the steel shaft ("2nd shaft"). So the slanted lever and the blade holders being the wrong way round will stay unchanged, that is uncorrected. (By the way, the six drawings are borrowed from the instruction manuals for the HIROBO S-300 and Lama, respectively.)
Once it was clear which modifications are needed to reverse the main rotor's sense of rotation, they had to be incorporated into the assembly process – in addition to the modifications for the three-blade rotor, which are specified in a separate manual. Electric conversion simply meant leaving out all parts specific to a glow engine drive and installing the electric motor with the special parts made for that by TMRF.
The pinion, dowelled on the clamping sleeve, has to be put on the motor's shaft journal so that its teeth are exactly at the same level as those of the cogwheel – that has to be measured and tested before installation. The black thing in the clamping sleeve is the setscrew which fixes the sleeve in place. The motor's shaft journal was flattened for such a screw and the shaft journal's length (23.5 mm) was adequate – no further treatment needed.
The motor's sense of rotation can be reversed by (1) interchanging two of the three leads to the ESC or (2) setting an ESC parameter – just as you like.
The KONTRONIK Pyro 600-09 (kv 930) is an amazing motor and most warmly recommended by Rüdiger Feil. It weighs only 235 g but can yield up to 2 kW power. It can spin at up to 30,000 rpm, but it will be operated at only 15,000 rpm in this case. Of course, that is no reason for a discount. (Just kidding.)
The main frame is composed of two very precisely injection-molded, mirror-inverted plastic parts, which require only very little dressing and buffing. Five ball-bearings are inserted into one of them and then both halves are tightly joined up with quite a few screws. All of these screws are neatly enumerated in the instruction manual lest we forget but one of them. A very small warpage (probably due to cooling down after the injection-molding) has vanished now and the frame is very solid and absolutely straight.
On the frame's rear (on the right in the picture) protrudes the journal of the tail rotor drive's shaft. Not visible here, the bevel gear pinion is already fitted to it.
The two aluminum stubs on the frame's lower rear side and the molded stubs at the tail rotor shaft's level are mounting points for the tail boom struts. The long aluminum rods on the frame's top will later hold the "scale" dummy fuel tanks.
The "bell" in the frame's center is actually the cooling fan housing for the glow engine – here it lends itself to be the electric motor's mount.
Here is the motor – properly centered and absolutely secure – bolted to the steel sheet disks especially made by TMRF Rüdiger Feil. The stub on the pinion's top is guided in a ball bearing so the gear's backlash is correct.
Bolted on top of the bull gear is the tail rotor drive's bevel bull gear, exactly aligned as well. The autorotation clutch – "reversed" here – is bolted together with the two bull gears so in case of autorotation the tail rotor will not spin (alas – I'd prefer it would).
Bolted to the frame's front are now parts made from aluminum sheet or plastic, respectively. They are meant to hold the servos in special trays and the rest of the R/C gear as one sees fit. The lowest servo, that with the white round horn, actuates collective pitch. For the three-blade rotor, the pushrod has to be mounted in the lower hole of the big aluminum lever. I also reversed the servo's horn and sense of rotation, simply because I deem that better in this case.
Between the big aluminum lever's upper right end and that of its counterpart on the other side is an axle. At its left and right end sits one roll-control lever each, and centered on it (between both aluminum levers) sits one pitch-control lever. So the whole thing is the mechanical mixer mentioned above, or it's several mixers, for that matter.
I hope the swashplate linkage is visible here, as well as the swashplate driver (called radius arm by HIROBO), the pitch-arm linkage for counterclockwise sense of rotation, and the rigid three-blade rotor head. The servo without horn on the left side will later actuate the tail rotor's pitch by means of a Bowden cable.
The servo horns are not yet bolted here so I can easily take them off. The linkages are adjusted by turning the ball links on the pushrods, and instead of pulling out and pressing in the balls I prefer taking the horn off. To adjust roll control, the ball links have to be taken off the horn in addition.
It's possible to put the whole thing sidewise on a desk without damaging the linkages – they are protected by the parts protruding sideways.
The instruction manuals specify the required lever arm length for every single servo, in fact different values for the three-blade rotor. HIROBO puzzled things out to a T and had to wangle again so all linkages are clear from each other and don't rub against anything.
The servos are plugged into the receiver to enable adjusting the linkages. Later they will be plugged into the "flybarless" system (microbeast) and the receiver is connected by one lead for composite signal. The white twisted lead on the base plate belongs to the telemetry temperature sensor on the motor.
The black vertical rod behind the servos and the lugs on the base plate's left and right side will later hold the canopy.
The big round hole sideways through the whole frame is nearly exactly below the main rotor's center (just a bit further fore). I'll keep it clear and later use it to balance the completed helicopter.
Here you see that standard-size servos are needed. Rüdiger Feil said that "no super strong or fast" ones are needed but "just good digital standard servos" would be sufficient. Then I figured the Hitec HS-5495BH would be just right. Even though they are inexpensive (at least they were), they are good and strong and very precise. They have no metal gear (but Karbonite), but this helicopter is electrically powered and will not be shaken by a glow engine, so that's OK. And perhaps in 1995, when this model came out, even the best servos were not as good as these modern ones. In any case, their actuating power should suffice.
Still not completed…
Not yet flying…
The Bottom Line
… just as a few notes:
- Nice, prototypical model.
- Substantially and accurately built, good quality.
- Still mechanical mixers, but well done.
- Very good electric conversion.
- The main rotor's sense of rotation can be reversed to CCW.
- Alas, the tail rotor does not spin during autorotation.
To be continued…
HIROBO Japan web pages (English)
TMRF Rüdiger Feil web pages (German)
Web page by TMRF Rüdiger Feil about the HIROBO Schweizer 300 with options (German)
Web page by TMRF Rüdiger Feil about the electric conversion kit (German/English)
Web page by KONTRONIK about the Pyro 600-09 motor (English)
Web page by HITEC about the HS-5495BH servo (English)
Video of Ted Mason's electric three-blade HIROBO S-300 at YouTube
Flight video of another HIROBO S-300 (electric, three-blader) at YouTube
Flight video of yet another HIROBO S-300 (electric, three-blader) at YouTube
Build video of a HIROBO S-300 (glow engine, three-blader) at YouTube
Build video of a HIROBO S-300 (glow engine, two-blader) at YouTube
Flight video of a HIROBO S-300 (glow engine, two-blader) at YouTube
Because this model helicopter has a modern electric drive, it just has to be equipped with modern telemetry as well. At least it would be hard to ensure flight safety without telemetry:
The ESC is working as a governor here. The usual slider on the transmitter is now used to adjust the main rotor's set rotation speed instead of the motor's power. Rotor speed is held constant as long as the drive battery has a minimum voltage. (No matter what, the motor is powerful enough.) Just diminishing battery voltage, due to regular discharge during flight or for other reasons, won't cause any reduction of rotor speed and will thus go unnoticed.
In view of already short flight times of electrically powered model helicopters, their pilots take pains to get the most out of the drive battery. Power requirements can be quite different between flights. Squally wind or a jittery flying style need more power than usual because governor and flybarless system have to work hard then. Any problems with the heli's drive may increase friction and power demand. In any case, the battery will age rapidly since it is heavily loaded in a helicopter. At the end of its service life it will rapidly lose capacity, and as a result voltage badly drops even after a short flight time.
Taking such contingencies of battery drain and capacity into account would require a big safety margin in setting up the transmitter's throttle timer. Big uncertainty would mean an undue curtailment of flight duration so using the throttle timer would be unpractical. Gladly you'd allow yourself some telemetry, on top of the governor and the flybarless system. In any case, that's not really expensive today.
In this case, receiver and ESC provide even most of the desired values; just two extra sensors are used to monitor drive battery voltages as well as motor and battery temperatures, respectively. Something special is the FlightRecorder, which records the telemetry data so they can be analyzed later – possibly after an accident.
Most of the values are not just recorded and transmitted but also monitored for exceeding or falling below adjustable limits. Values and any "alarms" are shown on transmitter displays and announced by a voice-output device. To be useful, both ways of rendering need a sensible setup and therefore I devise a coherent plan in the form of a spreadsheet.
On the Multiplex Sensor Bus (MSB), every value to be transmitted is assigned a unique address, which is its line number in the transmitter display as well. My transmitter has an integrated display and an ancillary one. The former automatically branches to a three-line "page" in case an "alarm" is triggered by one of the values on this page. The latter always shows the same four-line page as long as I don't scroll to another one. That's why I try to make up four-line pages with values which I want to monitor simultaneously. Then, the three-line pages are composed, as good as possible, by properly sequencing the values in the four-line pages:
These are the basic telemetry device settings. Up to 16 values may be transmitted on the MSB; the display sequence (leftmost column) follows from the selected bus addresses (fourth column). The four-line pages are marked off by black lines, the three-line pages by red lines. Alarm means optional upper and lower alarm thresholds while Parameters are mandatory and have to be set in the respective devices.
Only 10 of the possible 16 values are used here, an eleventh one just because there is still so much room. That's also why the two values delivered by the receiver have been left in their default places 0 and 1. For a 2s LiPo receiver battery, 7.4V under load is a safe warning (or alarm) threshold because it implies there is enough charge left for landing. "Priority off" means none of the values (or addresses) is transmitted more frequently than the others – that would be actually used just for a high-resolution variometer tone.
The main rotor's speed has been put in place 3, the last line of the first four-line page, so it appears in the first line of the second three-line page as well. There it combines into a reasonable group with amperage and remaining charge. Number of motor poles and gear ratio have to be specified because rotor rpm is derived from the motor's field frequency by calculation.
In turn, amperage and remaining charge combine into a reasonable four-line page together with battery voltage and lowest cell voltage. The ESC has a high-amperage warning threshold preset to 100% of its rating, which is 100A in this case. The 6s 7000mAh LiPo battery is charged to 4.15V (instead of 4.20V) per cell, which is why only 6750 is specified as capacity. 30% remaining charge, that is 2100mAh, is set as warning threshold. When the battery ages and wears out, less capacity has to be specified or a higher warning threshold. I prefer the latter but unfortunately both ways are equally inconvenient with the MSB. The 4.1V reset voltage (slightly lower than 4.15V) is used by the ESC to recognize a full LiPo battery and its cell count.
Immediately after the drive battery has been plugged and armed, the special voltage sensor checks its cell voltages. If one of them is below the value characteristic for LiPo cells charged "80%", a warning is issued – a safety feature. Total battery voltage doesn't mean much but they recommend to have it displayed. In this case, if the 3.4V cell voltage threshold (set here) is underrun, the respective warning is displayed in the place of total voltage. Only the so-called absolute low-voltage alarm (threshold 3.1V preset for LiPo) is shown in the place of cell voltage. The 3.4V warning threshold is the default value and is tried and trusted by me – and it's not too high. It should be even raised when the battery ages and wears out, but again that's rather inconvenient. If the sensor knows the amperage value's address ("4"), it can refrain from issuing a low-voltage warning in case of short amperage peaks.
Battery voltage and lowest cell voltage combine into a reasonable next three-line page with the following voltage as measured by the ESC – all three voltage values together. The last of them is the eleventh value mentioned above and is actually redundant because it will hardly differ from the first. Consequentially, its low-voltage warning is off. It's just a filler value here and on the next four-line page as well.
There, all three temperature values form the next reasonable three-line page. The motor is specified to withstand up to 150°C, but I set only 100°C as warning threshold because the sensor is not in the motor but simply clamped to its case. Coldness does no harm to the motor so its low-temperature warning threshold is off. The ESC has a predefined 100°C high-temperature warning threshold. The battery has the sensor just clamped to it like the motor, which is why I set 50°C and 5°C thresholds whereas internal battery temperatures should be kept between 60°C and 0°C. The lower threshold is on the off chance that the helicopter is outdoors in freezing temperatures and the battery cools off. Considering the existing safety buffers in the drive, it would be odd if a temperature alarm would really occur. The three values are interesting rather for later evaluation.
In this case, arranging all values in three-line and four-line pages worked out unusually well. That's not pointless even though I'll hardly look at a display while I'm flying the helicopter. But a clubmate could stand next to me and keep a close eye on both displays, and when the helicopter is adjusted on the ground I can even look myself. The reasonable and clear arrangement of values should help discerning the helicopter's "state of health".
My ROYALpro9 transmitter, bought in 2008, has no built-in voice output. For such cases, Multiplex brought out a special voice-output device, the Souffleur (Prompter in English). It has only five configuration memories, which are probably meant for different kinds of models. But I can get along with them even though I'm using them for individual model setups. The S-300 is my only helicopter with telemetry, anyway.
The voice-output setup follows from the basic settings. For every used bus address, type and frequency of announcements can be specified. The fifth column defines whether announcements are spoken in case of an alarm and/or periodically. In the third and fourth column, periodical announcements are made dependent on a transmitter switch setting. Info words are spoken prior to the respective value to make it distinguishable.
Amperage and remaining charge are obvious without info word because every announcement consists of a value and its unit. Main rotor speed is obvious for its unique unit as well, but I just want to have an info word here. The LQI's info word is preset and can't be removed, anyway (hence grey). All other values are voltages or temperatures and thus need an info word to tell them apart.
Info word, value, and unit – it takes some time to voice all that. Periodical announcements may easily clutter the voice output and that's why I want to hear most of them on demand only. With a transmitter switch (Servo 9) I can demand two groups of values: in center position (1.5ms), rotor speed, amperage, and battery voltage are called to be voiced every 30 seconds (Timer2); in top position (1.0ms) three temperatures every 30 seconds as well. None but remaining charge and cell voltage matter so much to me that they are always voiced, regardless of switch position, although just every 2 minutes (Timer1).
Almost all values are voiced if they exceed or fall below some threshold, in that case even with a preceded "Attention!". That may clutter the voice output as well and that's why I set all "alarms" to "single". The other option, "permanent", would mean an alarm is permanently spoken and hence nothing else (or nothing at all) can be recognized. That did not prove feasible, to say the least, and I don't see a reasonable usage, either.
So in case a temperature threshold is exceeded, the respective alarm is output only once. But that ought to alert me, and if I want to monitor the temperature further on I can flip said switch to its top position. That will call the three temperatures immediately and once again every 30 seconds. Alternatively, I can flip the switch up and instantly back down to call the values only once, and I can repeat that at random intervals. It would be hard not to voice even three temperatures in one chunk; after all several switches for voice output would be too complicated just in a distressing situation. But the three temperatures are interrelated, anyway, and if one of them is too high the other two may be worth knowing as well.
Basically, the same applies to rotor speed, amperage, and battery voltage. But for the former and the latter, no alarms are provided by the respective sensors. Perhaps rotor speed is seen as a mere effect of the two other factors, and with the ESC working as a governor it is maintained constant, anyway. However, instead of total battery voltage, the lowest cell voltage is monitored, which is more important and whose limit values are more easily remembered than those of a number of cells.
Receiver voltage and LQI are voiced as an alarm but not periodically, so only if problems arise. These are made as unlikely as possible by maintaining the battery and by properly orienting the antennas, respectively. By means of large capacity and short distance to the transmitter, respectively, both have quite a safety buffer.
The voltages measured by the ESC and by the special sensor on the battery should be equal. Just because there was a convenient place, both values have been included in the display. The former voltage is not voiced, though, because it's redundant and therefore becomes subject to the necessary axing of announcements.
After all it should be clear now that voice output significantly contributes to flight safety. While flying a helicopter, we hardly have time to look on a display – not only but especially in case an alarm is just signalized by sounding a beep. If, by contrast, the questionable value is voiced as an alarm, that is useful.
The FlightRecorder records all telemetry data (ten times a second) to have them analyzed later by a computer and this way see them in context and over the whole time of a flight. Especially after accidents it would be helpful to see the drive data also related to the heli's movements and the control inputs. The latter can't be recorded, though.
A sensor with a Prandtl tube could provide at least altitude, its change (variometer), and airspeed. In a model helicopter, though, which is flown at low altitude and at slow speed, it would be not really useful because its precision or resolution, respectively, is not up to the task. It just wouldn't be worth it.
At a first glance, a GPS could provide all movement data, and it would be even possible to plot the whole flight path three-dimensionally and including speeds. However, considering the performance of the GPS in my Senior Telemaster Plus (see here), it seems that a GPS is precise as long as it's in motion but produces erratic values when standing still. Hence, a model helicopter which spends a lot of time in hover flight seems to be not exactly a typical use case.
So basically, only drive data are recorded during flights. (A distinctive counter-example is the mentioned airplane – my Senior Telemaster Plus.) Nevertheless, a GPS will be tried in this helicopter, just because it's possible and simply to see how good or bad it works. In this case it will be set to "slow aircraft", though, in order to possibly avoid the erratic values which occurred in the other case. (That means horizontal speeds up to 79 km/h and vertical speeds up to 54 km/h, and this helicopter should stay in that range.)
The GPS 3D location data are logged by the FlightRecorder in any case. They are used to render a flight path in Google Earth. In diagrams, speed and altitude and perhaps also distance are useful data to plot over time. These have to be displayed (sent on the MSB) during flight so that the FlightRecorder can log them.
While flying a helicopter, such values should be hardly of any interest. Distance may be an exception, which is why it has been put into the former gap (place 2). Here it's indeed a meanigful complement on the first three-line as well as four-line page. "3D" means spatial distance, that is in the line of sight and not on the ground and seems to be more reasonable in case of a helicopter.
Speed and altitude have been just appended to the other values (places 12 to 14) but yet constitute a meaningful three-line as well as four-line page. Again, "3D" means spatial or in the line of sight while "2D" means on the ground. The former speed includes vertical speed (variometer), which is not separately displayed by the GPS. Both speeds are relative to the ground, that is not to the air, and a comparison gives at least a clue of vertical speed.
No warning thresholds have been set for the GPS values. Warnings are not needed during flight because this helicopter will be flown only slowly and at close range (as well as low altitude). So because warnings are pointless they would be even annoying. GPS values should be just logged for future reference.
Since no warnings are needed for GPS values and no announcements by voice, either, there are no changes or additions to the voice output setup.