glide speeds

[Hildy]

Scenario: you have 2L of fuel left, in tiger territory, and going to make a precautionary landing.

 

Do you:

 

- climb at Vy then glide at Vbg once the fuel cuts out

 

- climb at Vbg until the fuel cuts out, then glide at Vbg

 

- cruise at Vbg, then glide at Vbg

 

Vbg has the lowest drag, but Vy has the most power available (and presumably the best efficiency from the prop). in most planes they're pretty similar, but you can imagine a plane with an ultra-climb prop that has Vy much lower than Vbg.

 

the crazy idea I had today:

 

- auxiliary electric power hybrid plane.

 

this comes from the electric lazair thread:

 

if you have a plane with a 55HP main engine, could you put a second centreline thrust electric engine of about 10HP capacity, and enough batteries for 15 minutes of operation, and maybe 20HP in a life or death situation (the engine will overheat and need to be rebuilt, etc).

 

the two scenarios where this engine would be turned on:

 

- at takeoff, to make EFATO a less scary situation because you still have some thrust (especially if tuned for the right speed)

 

- in flight engine failure - to get some extra height or thrust at the right moment

 

- airbrakes on final approach - used to recharge the batteries

 

this system would weight about 10-15kg or about the same as a ballistic chute.

 

 

[Guest ozzie]

Not crazy they are working on Hybrids that will work the same as the automotive ones. Full time electric with small petrol engine to recharge.

 

As for the scenario i'd go for minimum power to stay in the air till i find a decent place to put down. When worst came to worst i'd make sure i had a bit of fuel for the approach and power stall if i had to if landing in area with no room for rollout, into trees ect.

 

 

[skyfox1]

Hi l would put in long range tank so you hopefully never get in that situation.

 

 

[Guest ozzie]

This situation could possibly happen with the weight restrictions on some of the aircraft out there. Is it going to take someone getting killed to get this mess sorted out. Like the sign at the that well known Pub says., "Free beer tomorrrow".

 

 

[farri]

Scenario: you have 2L of fuel left, in tiger territory, and going to make a precautionary landing.

Hi Hildy!

 

My definition of tiger country/territory is an area where there is no possibility of doing a safe landing or being able to glide clear of, in the event that a landing is required!

 

My question! Where are you going to carry out your Precautionary Landing?

 

Frank.

[Guest Andys@coffs]

also, understanding what you'll do in terms of what speedsfor descent, or climb, needs an understanding of the landing site with reference to the aircraft, your height and the prevailing winds. Obviously the answer will be very different if your over the top of the landing place, and entirely mute if its unreachable no matter what you do.

 

For me, not sure of others, when I was learning and had to practise emergency landings I found that at height to say, I'll land exactly in that field over there, 20 m beyond the fence, was damn hard to achieve, at least 90% of the time I was carrying too much height. The lesson for me was trying to force an aircraft to land in a position when you arent established correctly on finals is bad squared. In SA, where I learnt the rule was be flexible (because there were heaps of options), if when you are closer to the ground, it can be seen that paddock B is now a much better option than Paddock A then go with B. Too many, it seems to me make the determination at height that A's it, and then do their worst to make it so.

 

Andy

 

BTW it may be a terminology thing but I wouldnt call the scenario you described a precautionary landing at all. With the fuel contents you have described its a full on emergency one that you cant even go close to guarenteeing an ability to go around. about 10L earlier I would have agred with precautionary.

 

 

[Guest davidh10]

Can't help agreeing with Farri. You are already in a "mayday" scenario and it won't be a precautionary landing, but rather a controlled crash.

 

In that scenario, there are no rules of thumb that will apply to all circumstances, but you have some minutes to choose your crash site and the manner of the crash. You have to make your decisions based on the terrain and obstacles around you and what will minimse the harm to the occupants. That means sacrificing the aircraft if need be.

 

Based on the best crash advice, "...fly the aircraft right into the crash." That means having power to control the manner of arrival.

 

 

[Guest basscheffers]

The gauge won't be precise enough to tell you you only have two liters left. Even a fuel computer with flow sensor won't be that precise.

 

So the only way you can know you are that low is if you have been keeping an eye on the clock. In which case you should have known 15 minutes ago you only had 20 minutes left.

 

That would have been a great time to start looking for (and enquiring by radio) precautionary landing sites where you would still have enough time to do an inspection before committing.

 

Even where there is no strip you could save the aircraft, you may well find something less lethal anyway. (that might lose you your wings, or run into something on the ground - instead of in the air - at lower speeds)

 

 

[Guest SAJabiruflyer]

I think the best solution would be to quickly jumpy on your iPhone and post a new thread on Recreational Flying, and watch the debate evolve until you get an answer you are comfortable with. :)

 

 

[willatodd]

well im cheating coz it would be in a gyro but fly till you found the softest looking trees then get low and slow as you can in a gyro then a controlled vertical descent onto the trees. and climb at best rate for as long as i could finding those trees

 

 

[Guest Andys@coffs]

most people to climb use full power. In my aircraft that can easily move from 22 lts per hr to 40lts per hour with the resultant increase providing the up component. I would have guessed, with out knowing for sure, that almost twice as long in cruise is going to give me more options. For me, assuming the 2lts is usable fuel that represents just under 5.5 minutes at cruise at 120kts or 11nm before the glide commences.

 

On the otherhand climbing at 70kts, and say 800ftper minute I'll get 3 minutes or 3.5nm before glide starts but will be an extra 2400ft higher. According to my POH best speed for maximum distance glide (assuming zero wind) is 65kts. I cant find out what the resultant descent rate is, engine off, but im going to assume its around 600fpm at mauw. So that buys me another 4minutes, but at 65kts that allows me to cover another 4.3nm. so adding both its 7.8nm vs 11nm.

 

That being the case the only time that I might be tempted to climb is if im low down and cant see anywhere appropraite to land. We all know how much improvement there is with visibility if you climb from 500ft to 2500 above land. That said, if it is tiger country then what the hell was I doing so low with no options in the first place, and while I might want to climb as Bas inferred its just a bit too late in the game to be sure of an outcome.

 

That said, if I was truely over tiger country, and couldnt be clear in 11nm then I deserve what ever happens to me, cause 11nm is a long way especially when you then have glide ontop of that.

 

Andy

 

 

[Guest Andys@coffs]

I think the best solution would be to quickly jumpy on your iPhone and post a new thread on Recreational Flying, and watch the debate evolve until you get an answer you are comfortable with. :)

But only if the carrier is telstra otherwise you'll wste that 2lts trying to get coverage, in which case (3G) you should have climbed...

 

 

[facthunter]

One very important consideration is WHEN possible land while you still have power. You can do a much better job of putting a plane down in poor conditions with power still available. Another thing is TIGER country. You should avoid it whenever possible. You do this by

 

(a) going round it.

 

(b) Achieving a high cruise level by such means as climbing in a spiral over a suitable emergency landing area, so that you can glide clear of the "tiger" country. if you choose to cross over it. There's an old saying that has relevence. " Don't fly over what you can't land on". ..

 

( You should not therefore end up in the situation you describe if you manage your flight properly)..Certainly not compound your bad practices by not having enough fuel as well as getting into the situation where losing engine power puts you in circumstances where you would have a significant likelihood of being injured or killed... Nev

 

 

[eightyknots]

If there's only two litres in the tank, a steep climb may move the fuel away from the pickup point and the engine will cut during the climb.

 

I feel sorry for the tigers below.

 

 

[Steve Donald]

Scenario: you have 2L of fuel left, in tiger territory, and going to make a precautionary landing.Do you:

 

- climb at Vy then glide at Vbg once the fuel cuts out

 

- climb at Vbg until the fuel cuts out, then glide at Vbg

 

- cruise at Vbg, then glide at Vbg

 

Vbg has the lowest drag, but Vy has the most power available (and presumably the best efficiency from the prop). in most planes they're pretty similar, but you can imagine a plane with an ultra-climb prop that has Vy much lower than Vbg.

 

the crazy idea I had today:

 

- auxiliary electric power hybrid plane.

 

this comes from the electric lazair thread:

 

if you have a plane with a 55HP main engine, could you put a second centreline thrust electric engine of about 10HP capacity, and enough batteries for 15 minutes of operation, and maybe 20HP in a life or death situation (the engine will overheat and need to be rebuilt, etc).

 

the two scenarios where this engine would be turned on:

 

- at takeoff, to make EFATO a less scary situation because you still have some thrust (especially if tuned for the right speed)

 

- in flight engine failure - to get some extra height or thrust at the right moment

 

- airbrakes on final approach - used to recharge the batteries

 

this system would weight about 10-15kg or about the same as a ballistic chute.

2L GIVES YOU ENOUGH TIME TO TEXT ALL YOUR FRIENDS AND SAY GOODBYE AND SAY SORRY TO YOUR INSTRUCTOR FOR NOT PAYING ATTENTION IN CLASS.