diff --git a/.gitmodules b/.gitmodules
index 5adf946..5674c31 100644
--- a/.gitmodules
+++ b/.gitmodules
@@ -85,3 +85,9 @@
 [submodule "abritorch"]
 	path = abritorch
 	url = https://github.com/Ezhh/abritorch
+[submodule "minetest_biofuel"]
+	path = minetest_biofuel
+	url = https://github.com/APercy/minetest_biofuel
+[submodule "helicopter"]
+	path = helicopter
+	url = https://github.com/APercy/helicopter
diff --git a/helicopter b/helicopter
new file mode 160000
index 0000000..1955cdd
--- /dev/null
+++ b/helicopter
@@ -0,0 +1 @@
+Subproject commit 1955cdd71acefafa1023cbf80794793c5b9eb9b1
diff --git a/minetest_biofuel b/minetest_biofuel
new file mode 160000
index 0000000..ca480ce
--- /dev/null
+++ b/minetest_biofuel
@@ -0,0 +1 @@
+Subproject commit ca480ce750391c7569d2cf6b8f5c0d966d08bd45