A_and_C wrote:
Most pilots who fly jets take pride in planning their decent to avoid using the speed brakes…….. but they don’t have engine shock cooling to deal with.
Indeed they do, but that’s because it causes a lot of vibration ans wakes paxes up…
I think all Piper PA46 Mirages have speed brakes.
Engine cooling is not the only problem with going too low on power. You would also start losing losing cabin pressurisation. On low power setting turbos don’t spin fast enough to pump air to cabin.
Descending at around 165 IAS and 25 MAP without speed brakes gives -650 fpm and speed brakes doubles it. Usually you would plan descent so that you don’t need to deploy speedbrakes but quite often during your descent ATC wants to keep you at some altitude before clearing you again lower. In this situation I will deploy speedbrakes to get back to my planned profile. This way I don’t need to reduce power below 25 MAP to prevent engine cooling.
Jodel DR1050s have speed brakes below wings but not flaps. I only used them to reduce ground run, they appeared to make a slight difference. I sideslipped by preference to lose height. The speedbrakes had an 81 knot limit.
(22/12/20 was my last DR1050 flight.)
LowTimePilot wrote:
I think all Piper PA46 Mirages have speed brakes.
All PA-46 (not only Mirages) have a massive set of speed brakes factory installed. They are operated by the lever labeled “Gears” on the panel. With those 3 speed brakes deployed it feels like having to drag a chute behind you.
There are STCs to add another 2 comparatively tiny speed brakes on the top side of the wing (the free standard speed brakes are on the bottom of the plane) – I never understood what the additional benefit of those would be…
:-D the only “problem” with these “speed brakes” is that while you can extend the gear while anywhere in the green arc (Vle is about the same value as Vno) and then dive with almost Vne with it hanging out, you can’t retract it unless below 126 KIAS…
Other types do not have gear door attachments which are quite so robust, though.
Cobalt wrote:
:-D the only “problem” with these “speed brakes” is that while you can extend the gear while anywhere in the green arc (Vle is about the same value as Vno) and then dive with almost Vne with it hanging out, you can’t retract it unless below 126 KIAS…
Sure. From own experience I can tell that diving with those speed brakes extended at Vne give you such a large rate of descent as well as such an impressive nose down attitude that it is no practical limitation that you have to slow down to 126KIAS before retracting.
On a more serious note: Sure, unfortunately in many other retractable the Vle is so low that it is not practical to use the gears as speed brakes.
I guess they are very neat if you have to kill some speed fast. Especcially in clean wings like Mooneys or the Columbia, they can help to increase ROD without having to reduce power too much and they can be the solution to get down to gear speed in a hurry. Hence they are quite useful if you have an airplane which has low gear and flap speeds and are slippery constructions which are built for speed.
Even in my low powered C I had situations where speedbrakes would have been useful, e.g. coming in from the Julier Pass direct into Samedan is quite a descent which usually does not work as you don’t really have a level off during the whole thing. Either you drop the gear over the pass and come down all the way at below 120 mph or you circle at some stage.
I would not consider to have them retrofitted to anything below a K or J model and they are pretty much standard on the long bodies, with good reason.
In an old review of a Mooney 252, which I cannot seem to locate just now, I read the speed brakes give you 2 additional options: Descend at the same rate but 20 knots slower, or descend at the same speed but at twice the descend rate.
I recall in M20R Ovation it had two emergency descents and both give exactly the same -3000fpm ROD
1) Gear UP at 195kias VNE with airbreaks open
2) Gear DN at 165kias VLE with airbraks closed
The issue for 2) you have to slow down to 140kts to drop the gear before hitting 165kts again while for 1) you start from cruise speed
For both the real show stopped is “turbulent air flying” is 110kis while airbraks & gear don’t do much at those speeds compared to flaps (takeoff and climb with gear down & airbreaks open at 120kts will give more than 1200fpm, one can forget they are both extended)
I had them on the Corvalis and used them all the time on landing to manage the speed on the glide slope and reduce landing distance,
Don’t miss them in the Cirrus though.
With all respect, I’m not sure you need them on a TB20
