>>>That’s why I think a pilot needs to be terrain-aware at all times. But how many are? The technology for this is hardly mature.
Depends. The KGP-650 EGPWS System on the MFD the Cirrus (installed in a very high percentage of the fleet) is a very good tool for terrain awareness.
Jan_Olieslagers wrote:
Of course I have not the slightest idea about IFR flying, neither the underlying technological limitations nor the current implementation – which might excuse my posting hopelessly irrealistic expectations of applying available technology to optimise survivability.In the same spirit, I always approach fairly high, especially on shortish runways, and do “sideslip off” the excess altitude when close enough to be sure I’l make it to the runway even if the engine quits.
What I think you don’t appreciate is the importance of having a stabilised approach and of making very minute adjustments to correct your flight path. It would be next to impossible to fly an ILS (or corresponding GPS approach) using sideslips to adjust rate of descent. Maybe it could be made possible with different kinds of instruments, but I doubt it.
I guess it would work with the engine at idle if you had an airbrake to adjust the rate of descent. But how many GA aircraft (except gliders) have airbrakes?
This is the EGPWS/TAWS display of my Cirrus. The System is called KGP-650 and it contains a worldwide terrain and obstacle database. It shows the geometric GPS altitude o the left, your heading and the highes obstacles in a box on the upper right. 12(2) means that the highest obstacle in the RED sector 12.200 feet, 020 is the bottom elevation of the lowest color displayed, in this case the green color.
If I were to descend engine out in IMC I’d switch to the TAWS page on the MFD for the final descent. Of course it would be even better if the TAWS page was an overlay over the MAP … but my system can’t do that. It is still very helpful, for example if you get a route change over mountains flying in IMC … without a chart you can make sure you are clear of terrain, and will be.
This picture was made yesterday, flying towards the Alps in the Munich area.
I don’t see how that would help you glide into some canyon in the Alps, however.
I honestly don’t like to fly over overcast with below mountains, in addition I try to avoid as much areas with fog down to the ground I avoid it as much as I can. When do you become visual again when descending into a valley based on terrain data etc..?.Airfields are also very sparse with often very difficult approaches with obstacles. All big unknowns. I love SD and its always configured up and running as back up on my IFR flight, as you can select direct to nearest airfield and configure some kind of virtual localizer. The vertical profile can be adjusted I think to emulate an engine out angle of descent. Another option would be to adjust the virtual loc to a length that you know this is the distance altitude that you need to have in order to make it safely At least this would give you some kind of survivability in case the engine stops and you need to glide down. Assume that your FL100 engine quits and glide is 1/10 that’s 10 miles in the worst case. Given the speed and things never degrade from 100% to 0% I would not hesitate to elect any land-able VFR airfield within 15 Nm and stick with it till I am down safe! From my gliding experience it’s better to stick with your first choice then changing your plan at the last moment…..
Given the choice I would rather go for the VFR airfield even with a ceiling of 800 to 600 Ft then to push it to continue with an IFR approach with a potential complete engine failure during the approach and end up in a building…….
Peter wrote:
I don’t see how that would help you glide into some canyon in the Alps, however.
I’m not familiar with that Cirrus display but the Garmin 430/530 and our Honeywell Primus terrain displays are very similar. The colour coding changes depending on your relative altitude to the terrain. So when you are approaching the mountains while gliding from above, you will get a good idea where the valleys are and which direction is best avoided. I used this a lot when flying night freight with piston twins, especially out of Girona in summer, when an engine failure would have meant to be unable to maintain altitude, even at 5000ft. We always flew the departure routes with the terrain mode on to see the best escape route.
But as other said, all these fancy displays only help when you can see enough – and for long enough – once you come out of the cloud. Not even the fanciest synthetic vision system (including the ones using infrared cameras) will show you if the terrain ahead is suitable for landing and clear of obstacles. One single boulder or parked car or ditch will ruin your day. Therefore I repeat stuff I already wrote in previous threads by saying that for myself, I have set a cloud base limit of 1000ft for flying single-engine IFR. Only a parachute may convince me to accept anything lower than that.
With interest I have followed the “glideslope – style” discussions that Jan has led above. I think that I can see his point. What he means (correct me if I’m wrong) is that some kind of ILS pointer with a computed glideslope that takes into account the gliding properties of the aircraft could be a great help to do an optimum glide approach down to a safe landing. Ideally, the system would sense the engine failure and calculate which runway (or alternatively which piece of flat terrain) is within gliding range. It could then display some crosspointer or flight-director or “highway in the sky” style guidance right down to the landing spot. The technology to do that has been around since 35 years because this is how the Space Shuttle was guided. Today, it might even be possible to implement a simplified version on an iPad.
And regarding the “best glide speed” and “lowest sink rate” discussion:
1) If the engine fails in the middle of a flight, how do you know those speeds? They are dependent on mass (in my little Citation best glide speed varies as much as 30KT between MTOM and minimum mass!) and who calculates his mass and pulls out the table with speeds after his engine has just stopped in IMC? (This is one of the rare occasions where an AoA indicator really helps).
2) It would be a one-in-a-million-chance if the best suited landing site will be best reached at one of those speeds! In all other cases you will be either too low to reach that site, or too high. The best you can do if too low is to fly at minimum speed so that the impact is slowest. And if too high, you have to work off altitude and it does not matter the least at which speed you do that. The only reason (in my eyes) for flying best-gliding-range speed is when over sea or mountains so that you can glide as close to safety as possible.
I don’t see how that would help you glide into some canyon in the Alps, however.
Of course it would help, because it will show you the valleys in colors and all the obstacles on your way into the valley. The lower you get the better you will see the GREEN valley amdist the RED moutains!
The EGPWS system has prevented many CFIT accidents already.
It’s a completely different question if the pilot will have the nerve to glide into the valley looking at the MFD. I would use CAPS for sure … but I’d use it to glide to a valley first and then use the parachute.
If the engine fails in the middle of a flight, how do you know those speeds?
Well, with an SEP it’s not that complicated. The SR22 has a best glide speed of 88 KIAS (although I believe 100 POH gets me further, and this was confirmed by tests a US engineer did).
With my autopilot, this is what I would do: I find the nearest airport (GNS430: 3 turns to the right of the big right knob) … press DCT and ENTER and set the IAS to 100 KIAS. Descending I’d turn to the TAWS page on the MFD and check for obstacles and elevations on my way and if I was still in IMC at 2000 ft and/or completely sure I’d make the runway use CAPS.
The engine failure in IMC scenario was my main reason to go for an airplane with a chute … (but I had looked at a couple of 182s with BRS as well)
Well, with an SEP it’s not that complicated. The SR22 has a best glide speed of 88 KIAS
Aerodynamics and flight dynamics are the same for all aircraft (Space Shuttle and Concorde apart 
). The best glide angle (= greatest distance covered from a given height) is independet of mass, but the speed at which this angle is flown depends on mass. The 88KIAS from your manual most probably apply to MTOM because then it’s most critical. But at lower mass, you may get further flying at a different speed.
…With my autopilot…
If you have that luxury, you can try to do it the way you describe. Although I doubt that in the real situation you will not forget one or two items on your list… (I know that from my simulator trainings: Even when faced with “simple” emergencies that require only four or five actions one usually gets it wrong the first couple of times after not having trained for a year).
In many SEPs, especially the typical flying school workhorse or cheap charter aircraft, you won’t have the luxury of an autopilot in the first place. And even if you have one, it will fail at the same time as the suction becomes insufficient to drive the gyro instruments. You will need to hand-fly the aircraft with a limited panel (which most pilots will not have done after their initial IR training years ago) while working your Garmins and displays to find a landing spot and a safe route that leads there. And all that whilst maintaining a given speed and talking on the radio? Chuck Yeager maybe, but not us mortals…
As long as I’d have electrical power I’d let the A/P fly towards the NRST APT … secure the cabin, prepare for the rocket launch :-)
But I do know it’s all theory … One time I had SMOKE in the cabin of my Warrior (at 10.000 feet) and it’s interesting how my brain locked up … In the end it wasn’t dangerous because it was only brake fluid dripping into the hot cabin heater … but that was a pretty steep and quick descent believe me :-) I was sure I had electrical fire!
The 88 KIAS is for MTOM of course. But this value seems to be wrong, because tests showed that 100 KIAS works better at MTOM. I’d probably select something in between and leave it there …
I think: If the 88 is for MTOM, then for all lower speeds Vbg is lower than that, never faster. It will always glide the same distance though.
